A replacement Blu-Ray lens(lens by itself)runs around $70-80 now, so if you got the consoles pretty cheap you could try the repair yourself. As long as it's JUST the lens that's gone and you got the console for $100 or less, it's a steal of a deal.
If you weren't confident in your own skills to take apart the console, you could always ship off the broken one to Sony for $150 and they will repair it and give you a 90 day warranty for it.
Plus, what model are the ones you've been looking at? If it's a 20 or 60 gb model, then it's worth a bunch more, since those two are fully backwards compatible and no longer being made.