If its 40-2105 on flippers.com's website, I don't think $250 is totally out of line for this motor. Before Multiproducts stopped selling the old motors, we had to pay $250 each and a minimum order of 10 to get them to build any motor. And that was for a single frame motor, not sure what they would have wanted for a double frame unit. The days of a $75 M/P motor are long gone unless you get very lucky.
Not sure of the OP's budget or game condition but it seems that a number of these Midway games are very desirable and typically sell for north of $1000 when fully working. $250 to help complete a game is not out of line, not even for this cheap bastard doing the typing. I know John's pricing can be high at times but at least he has this old stuff and makes it available to others that a missing that one part to get their game functioning again. Steve at PBR does the same thing but his prices were typically much lower which is why he is not out of stock now on a lot of those kind of items.
If you are willing to sell one for less, I commend you!