Under the Crafting section of Between Adventures, the following reads:

"you make progress every day in 5 gp increments until you reach the market value of the item. For example, a suit of plate armor (market value 1,500 gp) takes 300 days to craft by yourself."

     However, the 5th edition Dungeon Master's Guide, page 129 stats the following on creating magic items;

" A character engaged in the crafting of a magic item makes progress in 25 gp increments, spending that amount for each day of work until the ·total cost is paid. The character is assumed to work for 8 hours each of those days. Thus, creating an uncommon magic item takes 20 days and 500 gp. You are free to adjust the costs to better suit your campaign."

     While adjustments to crafting times are necessary sometimes to move a game along or to bring characters who are crafting into availability, I felt the quote of 5 gp vs 25 gp increments was worth mentioning.

There is no conflict here, nor any typo.

There are two separate crafting rules in play; those for nonmagical items which progress is measured in 5 gp increments until completion, and those for magical items which progress is measured in 25 gp increments.

Ugh,... I just found this in the updated PHB.  This means that if someone wanted to create an enchanted Plate Armor of rare quality, they'd have to spend between 351-500 days crafting it.  This is much longer than I imagined the creation process being for magical items.  I always ran magical item production as a whole cost and not just the magical process.  Thank you for clearing this up for me.

I've always ran it as needing the piece of equipment to be enchanted as part of the raw materials. So in this case you would need the Armor either by buying it or creating it first, then applying to magic to it.

I'd have to dig through my books once I get home to see if that it RAW or just something I do.

Quote from Scryercloak >>

This is much longer than I imagined the creation process being for magical items.

Don't overlook that characters can work together to craft items, reducing the time taken dramatically.

For example, a party of 4 with at least 1 character with spell slots can make a rare magic item in just 25 days. And since the rules for making magic items don't force you to start with raw materials and make the item itself first, you can just buy plate armor and get a rare magical plate armor in far less than 351 days.

Quote from Scryercloak >>

Ugh,... I just found this in the updated PHB.  This means that if someone wanted to create an enchanted Plate Armor of rare quality, they'd have to spend between 351-500 days crafting it.  This is much longer than I imagined the creation process being for magical items.  I always ran magical item production as a whole cost and not just the magical process.  Thank you for clearing this up for me.

This is one of the things I house rule in my campaigns. Non-magical crafting I do at 25gp per day and magical item I do at 100gp per day (however some items I adjust for flavour, etc.).

Very true. While a single person would struggle, many successful weapon and armor shops have multiple smiths working behind them to keep up with demand.

I like your house rule, Sorce, as it makes it pretty easy to understand, but still means some effort it needed. I like how it is setup for multiple players or at DM's discretion NPCs can help get items made faster due to more manpower. This just makes sense as Scryercloak points out. Most shops have apprentices up to masters and bigger cities should have much larger shops.

I see no issues with a DM tweaking the rules to fit how their campaigns flow or ease of managing it as long as everyone is happy with it and it doesn't seem way off the beaten path of the original rule. This might be where we find a few misunderstandings when actually making sure we know a rule because we may be used to some combo of house rules and homebrewing depending on the DM we have.