I've been reading this thread with more than a bit of dismay and disbelief. It seems that very few Model M enthusiasts are willing to pay a fair price for a keyboard such as this one, really clean, fully functional, and bolt-modded by someone with substantial experience doing this work. It also seems like too many Model M fans think any price over $30 for a used Model M in clean, excellent condition is too much to pay. Let me clue you all in to something. Yes, you can find used Model M's probably fished out of a garbage dumpster (and looking like it) for $30. IME the average selling price for Model M's worth owning is usually between $50-100 + shipping, with occasional rare exceptions.
Years ago, around 1991 IIRC, I had to pay $250, plus a $25 handling charge to buy a new Model M from an IBM service depot back when these were not sold by IBM except with an IBM PC. I lied to the service depot folks, telling then I owned a PC/AT that had a failed keyboard and I needed a replacement; otherwise I couldn't have bought it at all. And I still felt damned lucky to own a Model M without having to buy a PC/AT -- even at that high a price.
If you start with a Model M that you got for free because you happen to be in the recycling business, it's no secret that you can afford to sell it for $30. But if you had to buy that keyboard (on eBay or elsewhere) and it's one of the nicer ones, and then you add about 3-4 hours or more of labor to thoroughly clean it inside and out, then bolt-mod it using high-quality stainless steel fasteners costing anywhere from $10-20 depending on how many you actually install, selling it for less than $100 means that you're effectively working for minimum-wage.
I've been collecting Model M's for some time now and currently have about 100 or so, about 1/3 of them being NIB and the rest used but in superb condition. I plan to offer these for resale in the near future. I plan to bolt-mod every one of them using USA-made stainless steel low-profile Torx-head screws. These screws cost about 35 cents each and there are 51 of them (if I counted correctly) -- I don't bolt the very last row in the front (under the spacebar, etc.) because doing so interferes with re-seating the keyswitch assembly back into the housing, and these front-row rivet positions are completely unnecessary anyway IMO. So far I've completed around 15 or so, with excellent results. These keyboards are also quite pristine in appearance, almost as nice as when they were new.
I'm planning to include a brand-new SDL cable (cost ~$20 each) and USB converter (cost ~10-15 each) with each keyboard, and am even converting the "attached-cable" M's to detachable SDL format by replacing the existing PCB header (that takes the attached cable) with an SDL receptacle since mounting holes, solder pads, and wiring for an SDL receptacle are also present on these controller boards.
Furthermore, I'm having custom 2-piece foam packing inserts made so these will be well-protected in shipment. The inserts will cost around $25 per set. Adding up all the costs and the labor, I find that I will have to get at least $175 for a typical 101-key Model M.
But now I'm wondering if I'll be able to sell these at that price level, no matter how good they are...
