OK, I just realised that to use the NVSRAM chips I'll have to decrease the number of banks to 4 instead of 8, or increase it to 16 banks, because Cypress (the sole manufacturer of this kind of SRAM) has graciously decided not to manufacture 512kb NVSRAMs. Yay! I am thinking 4 banks will be a better option simply because it simplifies bankswitching (which is done via actual switches, I might add) and reduces cost while keeping the 28 pin footprint (and pinout, huzzah!) that's already on the cartridge, which reduces labor involved.
If I increase to 16 banks well... that nearly triples the IC cost. And blows the whole "ease of use" thing. And the pinout. So the spec is changing- 4 banks. That's still a good deal of space, I should think.
Secondly, purchasing will be different this time. Because these have a substantially greater cost per unit than the Glitchnes cartridges I made before, I'll still be offering preorders but will require payment before I start building, simply because I don't have the cash to lay down to order parts, etc. for a dozen or more of these things. Keep in mind this will be a very small production run, assembled entirely by hand, by only me.
Lastly, I have nailed down the price. Given the amount of time I have put into my prototype (which is nearly completed) I can now estimate my personal contribution: the labor. Which means the price is going to be $85. If people are really really upset by this price I'll revise the specs or possibly offer units with less features.
Perhaps the only standard option I am considering at all is the omission of the multiple SRAM banks, instead leaving only the built in single SRAM bank which the donor cartridge ships with. This would substantially reduce cost, eliminating the single most expensive part and reducing labor somewhat.
If all goes as planned (IE, my chips ship) I will unveil my prototype and begin preorders this coming weekend. Keep in mind that preordering will most likely be limited to 26 units, absolute tops. Why 26 you may ask? It's the minimum multiple you can order these new Cypress NVSRAM chips in, and I don't want to make 52 cartridges.