In general, I think the answer should be no.
Feats are character defining characteristics every bit as much (if not more) than a class level. Allowing in game magic to directly give feats can have weird effects on game sensibility and balance.
There are lots of things that are superficially "fair deals" but are very dangerous to allow as a default rule in the campaign. How many wishes to buy a level? Immortality? Can I wish to swap my 15 Fighter levels for 15 Wizard levels?
I am not saying to never allow such things in your campaign, just as general rule they should not be allowed.
As for how much a feat is worth relative to a stat, I can buy a +1 Str boost for 1000 gp and a +2 Str boost for 4000 gp. A feat in an item is usually worth somewhere in the range of 5000 to 15000 at a guess. "Natural" feats could be priced at twice that as a slotless item.