Thats what i would say.
Tell him after doing research you know alot of work is required to get them healthy again.
Tell him 175.. if he says no, say 200 and make it a final offer.
If he says no, keep your money.
The only big concern is that you already have a collection (right?). I am very new to the BP world but mites dont exactly sound like a good time.
Bartering was invented for such situations as this.