This guy sounds dillusional. He wants a $90k premium on a $110k house? Only if the 30lb in gold bricks in the basement conveys.....
My thoughts (and feel free to ignore them, I'm a newbie) is that you need to figure how much it costs to get the nearest comp into the same condition as his place, all while figuring out what an acceptable profit and risk is for you. At the same time, is his place "over-improved" for the neighborhood? If there are no $200k comps in the neighborhood, this guy might be a little crazy. You can't negotiate with crazy.
But seriously, with that kind of difference, it sounds like it's tough. If you want to spend the time, meet him and go over comps and the benefit of signing a contract with you. If he doesn't like what you have to say, say "listen, it looks like it won't work out with what I have to offer, let me get you the names of a few Realtors who are well-respected/trusted/liked/hungry and who work with properties like this. It's likely going to take more time to sell, but you may be able to get a better offer." Then, walk away and call back in a few weeks.
Not speaking from experience in real estate because I haven't done any wholesaling, but this is my thought based on my negotiations as a lawyer. If there is too much of a gap between the parties, work on building trust, the ability to walk away, and circling back.