First of all, dictionaries list both spellings, and pricy is generally listed as a variant spelling of pricey, not the other way round, at least in the dictionaries I have checked (Merriam-Webster, Wiktionary, New Oxford American Dictionary, American Heritage Dictionary, Cambridge Dictionaries Online).
Secondly, the usage stats from the Corpus of Contemporary American English (COCA) and the British National Corpus (BNC) look as follows:
pricey 1421 73
pricy 36 4
As you can see, this is not an American vs. British English thing. Pricey is clearly more popular on both sides of the pond.
Furthermore, the Corpus of Historical American English (COHA) paints the following picture:
(X axis: year, Y axis: absolute number of hits.)
So, this suggests three things, at least for American English:
- Both words are surprisingly recent coinages. COHA does return three more hits from 1837, 1928, and 1966,
but they all look like typos or OCR failures to me. Etymonline confirms: "1932, from price + -y".
- Pricey has always been more popular than pricy.
- Pricey is getting even more popular, while pricy fades in comparison.
So the bottom line is: both spellings are correct, but if you want to be on the safe side, pricey is the way to go.