Thinking out loud here,
If you are going to make them two piece, make the top easily come off for adjustments,etc. There has to be a happy medium on making them tall enough to clear rollers yet short enough to clear the ac box. Two piece, with say a 1 1/2" spacer and then a shorter top would let both sections be removed easily. Cost is going to scare off many regardless of how you do it, unless they get made in china, which would scare off more people than the american price tag. Send them with felpro's permadry plus gasket for the bottom and it won't leak. I would be in the market for something like that in the future when I go roller.