I want to have a potion available for my players that reduces a short rest to about 10 minutes. How rare/ valuable should this be? What level health potion would you compare it to in terms of Rarity/value? 

Crimson Minotaur gives you wings!

This is basically a Catnap effect and you balance the no need of sleep or use of spell slot with the targeting only 1 person so no need to balance-adjust further. It's 3rd level spell which would make it Uncommon rarity. I would, however, keep the clause that once used you cannot benefit from such a potion again until you complete a long rest - if you wish to drop that, make it Rare.

Nice, thanks man. Good tip in regards to the long rest.