That is so NOT worth $750.00 USD. Not even close.
Look, I'm the first one to recognize nice terrain when I see it, and this is nice terrain.
But I also know after years of making it what materials and techniques are required. It's not complicated. It's all mechanical and technical. You cut and sand foam. You texture and paint it. You make a framework for the board surface.
It's not artistic unless you are literally creating some sort of unique building that has hand-painted designs or some kind of unique, intricate details.
But THIS kind of terrain? I'm sorry, but I could make that in an afternoon, and actually make it look better than that does. That's got about $30.00 USD of materials and maybe five or six hours of labor. Seriously. So if this person expects someone to pay them about $107 USD an hour for this project – I would advise that potential buyer to learn how to make this kind of terrain themselves!
No disrespect meant at all. But this is seriously basic terrain.