That second hand phone is still sim locked, you'd still have to crack it. I'd rather crack a new phone and hopefully have a better chance of it not failing than buy one second hand (pre-cracked or not) and have it fail the day after and still have no recourse.

For something that's used as much as a phone is, and for something as non user repairable, for me it would be a huge gamble. My old Nokia N95 still works but if it went on ebay I doubt I'd bid more than a tenner on it.

I suppose if people are idiotic enough to want to spend sums of money like that on phones with absolutely no warranties on them then so be it.