Well, one thing is for sure, you will have to spend a lot of time to take any of those razors and turn it into something that can compare with a brand new $80 carbon steeled DOVO which takes about five minutes of honing/stropping to make good.
So how much should you pay. Given your investment in tools and your time at say $40 per hour. Also if you need to sell them, their sales value, your time to photograph and sell them including packing and posting.
Well financially, I don't think your going to make much money if you get them for free.
But if it's a hobby, I'd pay no more than $250.