Edmund,
The inkjet guys really are experts at making ... inkjets. I'm sure that if they wanted to they could do an iSis or DTP70 equivalent for $50 plus the price of a spectro head. They might have spectro issues but not jamming issues, by now jamming issues are zilch on the better Epson and Canons and you know how much they sell for :)
The price of the scanning spectros has a lot to do with market segmentation, and the fact that the mechanics are bespoke. Canon and Epson make that stuff every day, their engineering investment would be much lower.
But the price of desktop printers has a great deal to do with the fact that the manufacturers are giving you the platform to get you on the hook for buying consumables. There wouldn't be any consumables to buy in this device. Then you'd have the cost of the spectro head, and the licensing fee, and the pretty small size of the prospective market, and I really can't see this costing any less than an Isis.