Is it so that when doing rebates Canon raises prices at the same time, or is it the stores taking advantage of the rebate and "stealing" half of it by raising their price?
A couple of years ago, Canon started requiring a 'minimum advertised price' by their authorized dealers during rebates. Effectively, it reduces the value of the rebate, in some cases quite a bit.
Some retailers (Adorama and Amazon, for example) seem to take a day or so to raise the prices, so if you order in the first few hours the rebate is available, you get the rebate applied to the lower street price.