body - What sets apart DSLRs in different price levels?

I was going through different models of Canon and found that the price range of the camera body for entry level DSLR is lesser than the semi-professional DSLR although both of these range of cameras offer the same specification, same pixel count etc.

• So, what is the logic behind the phenomenal price gap even though the specs are same?


• Coming to the next question, keeping in view that the specs are alike, should I go for a cheaper camera body so that I can invest more on the lens? Or does a higher price tag essentially mean better a camera?


• Are lens compatible for any camera model for a particular brand say for example a lens EOS 60D would work for EOS 550?