Learn English – “Updatable” vs. “Updateable”: which is correct

Short answer: There's no clear choice; take your pick.

Long answer: Neither collideable nor collidable is a word you're likely to find in a dictionary, but in your context using it (one of them) may be exactly the right choice. As for the spelling preference, Wikipedia's detailed article on American and British English spelling differences says:

Before -able, British English prefers likeable, liveable, rateable, saleable, sizeable, unshakeable, where American practice prefers to drop the -e; [borderline: tradeable, smokeable, driveable, shareable] but both British and American English prefer breathable, curable, datable, lovable, movable, notable, provable, quotable, scalable, solvable, usable, and those where the root is polysyllabic, like believable or decidable. Both forms of the language retain the silent e when it is necessary to preserve a soft c, ch, or g, such as in traceable, cacheable, changeable; both usually retain the "e" after -dge, as in knowledgeable, unbridgeable, and unabridgeable. ("These rights are unabridgeable.")

The "polysyllabic" rule would point towards collidable, but elsewhere, a search brings up the following poly-syllabic words ending in eable (other than soft c, ch, g instances, of which there are many) (I haven't checked their provenance):

canoeable diagnoseable disagreeable dislikeable fireable foreseeable handleable hireable machineable microwaveable removeable settleable throttleable unforeseeable unnameable upgradeable whistleable

Or you may want to look specifically at -able words formed from verbs ending in -de, and decide whether -dable or -deable is preferable:

abradable codable decidable degradable dividable evadable excludable extrudable fadable gradable guidable hidable includable persuadable ridable/rideable slidable tradable/tradeable upgradable/upgradeable wadable/wadeable

It seems that analogy with dividable and decidable (the closest?) would suggest collidable. (But if you still prefer collideable, it's fine to use it…)

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:

            COCA   BNC

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:

1. 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".
2. Pricey has always been more popular than pricy.
3. 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.