Basically it comes down to 2 things:
1) Condition; if it is in excellent nick (ie. no noise) I'll take it...Last one, bought from a wrecker, was noisier than the one it replaced and their "30-day" warranty had expired. (As a side note, if you're in the ACT and are looking for parts, PM me and I'll give you an idea of at least one wrecker to avoid - That's for the wrecker in question...)
2) Cost to get it here - as that needs to be factored into what I pay for the thing.