if 150 is for piano score, conductor parts, a rehearsal score and all wind parts, that's a deal. wind music and std lit rearrangements will be within copyright are there's more than a fair amount of work involved in rescoring those things. it's worth it at 300, espeically if that's all 3 movements, but i'd pay 300 for everything even for a single movement.
You can likely borrow it for free. If you conductor can get with some librarian(s) and make some calls, i'm almost certain a music school, even a junior college/community college (lots of them have some respectable libraries, and a lot should have really good wind libraries). It could likely be loaned for free ot just the cost of shipping,.
if that doesn't work you can also look at a couple of good other pieces like this, i did the warsaw concerto w/ a wind band and it was awesome. There's a good one of the gershwin rhapsody in blue for piano and wind ensemble as well.