Money and logic

Where is the flaw in my logic. This seems like it should be flawed, but I can't find it.

I'm thinking of buying a normal cello from ebay on the theory that if I wait long enough for a good deal on the electric cello, I will save more on a good deal than I spend on the normal cello and then maybe I can sell the normal cello once I get the electric one, but even if I can't no money lots because current price - good deal price > normal cello price.

So... anyone see something stupid in that?