I got my bead blast cabinet at Harbor Freight for under $100. Its a bench top model, but I used 2x4s I had in the shop to build a stand with wheels. It was a nice unit; came with everything I needed including 4-5 different sized nozzles and extra plastic sheets to protect the glass viewing piece.
As for a compressor, I bought a 21 gallon from HF too. It was on sale for $150ish. I didnt expect it to last long, buts its been running a year with no problems. I use it for agitation and blasting. Sears sells a 175 psi 30 gallon for around $250-275 that I plan on buying next.
As for blasting, I buy my 80 grit glass beads at HF and blast at around 65 psi.
Oh, and mine says 5 lbs max too. I have about 25 in it
Been blasting this way for over a year with great results.