I wouldn't be able to build a substitute for a half decent brand-new manufactured keyboard for $88 if I got the parts for free. I've build some interesting musical keyboards but mostly because they had geometries that were non-standard and I'm still toying with the idea of making a complete action from scratch. But that's 'madman' territory, just as a challenge, not for cost savings.
Sorry I wasn't clear, I was think just the electronics at $1 per key. The action for the keyboard would cost more than that. In my alternate life I find a broken/disused KX-88 and rebuild its keyboard :-)
I repair DX-7's to keep them alive (usually three broken ones yield about two good ones and some spare bits), I can look for KX-88's while looking for DX-7s if you want.
I periodically search Craigslist for them and I've asked the local gear reseller (Starving Musician) to be on the eye out for a "dead" one. I seriously doubt having one shipped would be cost effective :-). There is a $50 one on Ebay in Illinois for local pickup.
