See post about gauntlets of ogre power. 

This is just so overpowered for any melee charecter, I don't understand why there aren't simular items for other key attributes 

Pretty much every other stat has many other uses.  Strength is for melee attacks, athletics, and that's almost it.  Every other stat (dex especially) either has a lot more uses (AC/int/more useful saves), or affects a lot more skills.

I love magic items in DnD. This stupid looking belt that only looks good if you make an entire outfit around it makes a kobold with a STR score of 6 hit with the force of a level 20 barbarian. It reminds me of this ProZD video: https://www.youtube.com/watch?v=xq1tN9jZI80

My paladin got one of these. Started with a STR of 8. Got it at level 2. Storm belt.

Oh, and in that same one-shot, he got a suit of plate.

Needless to say, he only got the one magic item.

My group find the fire geant belt but since i had the hand of Vecna already (starting strengh of 8 and finess weapon) a mere 20 is enough for me! I have plenty of other cools bonuses. But i wouldn't say no on a storm belt for maximal effet :)

How much would a Belt of Storm Giant Strength sell for? I'm pretty sure that the range for legendary items is 50,000+ gp, but how much would this specific item be? One, two hundred thousand? More? Less?

That depends on the setting details, really.

The default for magic items in 5e is that they are rarely sold or bought for gold and thus have no set prices. Especially the ones of such a high rarity and power. So unless your DM has made specific alterations to their game world's economy, it is highly unlikely that you will find a buyer for pure coin, considering that rarely anybody would have this amount available, and it would be nigh impossible to transport such an amount, even with a bag of holding.

And even if recompensed in other things, such as real estate, services, etc., there is always the question who would be willing to give this amount of worth in exchange for just a single magical item, powerful as it may be.

Since the character is a paladin, I could maybe just find someone who's willing to trade a Holy Avenger for it (preferably a non-paladin so they don't lose much by giving it up). However, I'm only level 3, and I don't want to be too overpowered. Any legendary item is too overpowered for level 3. Then again, the sorcerer in the party has a Ring of Three Wishes... even if it only has one charge left. If I were the DM, I would probably have it take a whole adventure just to find someone who will buy the belt, then let it sell for about 150,000 to 200,000, on the stipulation that the player couldn't buy a legendary item or artifact with the money, and enforce serious upkeep charges on the skyship they bought instead. In short, balance it. I'm obviously not the DM in this situation, but I know my dad (who is) will balance it.

The other three members of the party each got four or five magic items, but they weren't anywhere near legendary. Most were still very good (except for the Staff of Withering that none of us can attune to), but my Belt of Storm Giant Strength was the second best (after the Ring of Three Wishes).

Thanks!

To be fair, if he's handing out that kind and amount of treasure at that low of a level, most semblances of balances are out the window anyway, so you will probably find what you want.

Though I can only imagine how horribly broken encounters would be under these circumstances.

It was our first adventure, actually, and he just found a pre-written one-shot to run. We rolled randomly for loot. He is a fair DM, and in talking to him about it he said he would definitely make it hard to sell, if possible at all.

But yeah, the next many, many encounters will be soooooo unbalanced (in our favor, of course). Though I can imagine that he'd probably upscale them.

The problem about upscaling to compensate for something like this is, that whatever threatens you will potentially also one-shot you on a decent roll on these levels.

Not that it can't be fun now and then, but in the long run I feel like an over-saturation like this (and I am fairly certain rolling randomly for such a low encounter will not by the normal rules yield items of that power,  so I most definitely feel like there was some manipulation from the DM in your group's favor) leads to a lot of problems. But hey, as long as you're having fun with it, roll with it.

Since Stone Giant and Frost Giant strength belts are both very rare, but presumably there would be around the same number of each, would that basically make a STR 23 Belt of Giant's Strength (adding both together) into a Rare item instead of Very Rare? Counting the effect rather than the specific style of belt?

No imagine a ranged character like a wizard gets this and suddenly they can one shot anything they punch because they have 29 strength.

That's up to the GM

That doesn't really explain why they don't have an equivalent for Con.  its only used for hit points and saves, and even then, con saves are almost completely absent unless you're dealing with poison, cold, or necrotic damage

Con affects every single class and how you handle every single attack. Str is honestly mandatory only for barbarians with their rage mechanics. Everyone else can get away with dex.

I'm a 8th level character and I got a hill giant belt from a side quest that only had one encounter. Is that too big of a reward? (just wondering, I gonna keep it anyway).

It's a good roll on the random treasure tables, but totally feasible.

On another note, these are wonderful for clerics. She got to take feats and Constitution increases instead of investing in her Strength.

Quote from Trewill91 >>

That doesn't really explain why they don't have an equivalent for Con.  its only used for hit points and saves, and even then, con saves are almost completely absent unless you're dealing with poison, cold, or necrotic damage

Sure, Con Saves aren't common from spell effects, and as a fighter or barb, its not as useful as it could be on top of a 20th level barb needs the storm or cloud variant. A spellcaster however, gets a massive buff with any variant.

I'm gonna do a little theory crafting here. I'd guess a wizard's average con at max level is 14-16, maybe 12-16 depending on how they want to play. A barbarian would have somewhere around 20-24 at max level depending on how they have built themselves. Using the storm belt, a wizard would get 262 hp, and the barb with a maxed con would get 285. The barb will already be ******* hard to kill. The wizard becomes hard to take out themselves. On top of this the minimum damage required for a wizard to lose concentration on a spell is 24 damage, and this is on a nat 1. Assuming war caster which is a wizard's bread and butter, the odds of failing are low into the 40's. If I were going to build a wizard with the intent on going out of my way to find a cloud or storm variant, I would pick up war caster, resilient con, use a racial bonus and 2 ability score improvements to max my int using standard array, and use my last ability score on something like elemental adept, lucky, mobile, observant, alert, and the other super good utility or caster feats. 

Big point, the reason the con equivalent to the belts of giant strength don't exist is because the con belts wouldn't just benefit a melee user like the str belts ultimately do. Spellcasters would become terrifying with the con belts at all level ranges. It would become an item would be sought after by most players and have a ridiculous amount of utility across all characters, which is something WotC tries to avoid when it comes to magic items. This was longer than it needed to be but I wanted to prove a point, so I'm sorry that is super long winded