This is my version of a simple I/Q receiver (base) by YU1LM, the SDR2A if I remember well (that needs a sound card):

The price will be different based on the capabilities of the VFO (0 .. 4*f MHz), the quality of the operating amplifiers used, the mixer, which is mostly a Tayloe-mixer, you can look after it (but that will be cheap anyway), the number of bands you need (buying rings, switching over the bands), do you want to buy a kit or build an SDR with a transmitter as well, etc.
So, more input is needed about your requests/requirements.