Off the top of my head, this is a bare minimum:
co2 tank (5, 10, 20 lb) $50
co2 regulator $40
co2 gas hose $5
gas pinlock disconnect $8
liquid pinlock disconnect $8
liquid hose $7
liquid faucet $5
hose clamps $5
optionals:
O-rings $5
swivel nuts (need to match your disconnects) $10
This should allow you to carbonate and dispense a beverage using forced co2 carbonation (as opposed to conditioned carbonation like in a bottle). Something like $130 for the minimum needed depending on the prices you can find for yourself.