What is a fair price for 515E drivers?

I know someone who has half a dozen that are generally in good condition. The only bad thing is that they have two opposite sides of the basket fronts cut down slightly to fit some weird cinema install that they were in. They are parallel cuts straight through the bolt hole so there is still enough basket to mount them well, I think.

I see them on ebay for $500 each, but this seems high. Does anyone really pay that? What would a fair (to both parties) offer be?

Thanks.