To go from 2 million pixels (1080P) to 8 million pixels (4K) is a lot easier to do with a TV that has several square feet of space compared to a projector that has to fit that many more pixels in an area less than a square inch. They can make bigger chips but that requires bigger lenses which increases cost significantly. If they keep the chips the same size they trade off other picture qualities like contrast because smaller pixels means less light.

You will definitely see the E-shift and wobulation types of pseudo 4K become less expensive first. It will take a little while before we see true 4K projectors come down in price. I hope I am wrong.