You can get cheaper buttons than that at paradise arcade:
1.15 a piece for cheap knock-off happs buttons with 50g micros.
and get the xin mo from either ggg or paradise arcade for the encoder. its 25 bucks from paradise, 27 at GGG, if you want cheap, bare-bones its a better option because the ECO has a board you need to solder too, there are no connectors, where as the xin mo is a pre-made harness you plug in, so its less work.
so for 16 buttons, that's $18.40 cents, xin mo is 25 bucks. Shipping from Paradise is usually a flat 6 bucks or whatever the rate is for priority mail. so you are looking at about 50 bucks there.
You can probably get it all down to around 75 bucks after shipping