It's a little over $100, which isn't all that much when you consider that this is a CPU that has been used successfully in space before by NASA.
(I remember a short while ago on an electronics forum there was a discussion about either this or a similar project - can't remember - where someone bet that they were certainly going to fail because they weren't using rad-hard parts. This data point certainly supports that.)
Yes, that chip was used on the Galileo satellite but the Silicon-on-Sapphire version that NASA used for that mission is significantly more expensive. The $100 version has error correction built in but it's only rad hardening is any packaging and specs (low power + slow clock speed). A current generation rad hardened CPU comparable to the SOS version in the Galileo would be the RAD750 [1]. Several Arduinos in a lead box would be roughly equivalent to the consumer RCA 1802 chips.
I don't have exact numbers but from my limited experience I would say about 30% of the price is the cost of setup and production (human labor, materials, capital depreciation) and the rest of the price minus profit is administrative, sales, and regulatory cost. Silicon design is getting cheaper, especially with FPGAs, and the designs are relatively flexible while the sheer amount of time required to set up a manufacturing line to produce even a single processor is very expensive. Like the RCA 1802 linked above, a single silicon design can be used for decades in mission critical applications as the revenue piles up and the costs to tweak the design fall. When you're the only one buying a setup for a rad hardened manufacturing process and producing only a dozen chips for your client, slipping in several experimental revisions on the mask can sometimes be almost free.
Most compliance issues are barriers to entry but are largely overblown. In fields like aerospace and nuclear weapons the most critical requirement is abundant reliability and lifetime data which is why, regulation or no, you will never put something like an Intel 60nm or lower processor into a critical $100 million satellite.
I'm mostly wondering if there could be a business case (or hobby project) to make medium volumes of non custom rad hard chips for cost constrained aerospace projects.
Not really, depending on the performance you want:
http://www.intersil.com/en/products/space-and-harsh-environm...
It's a little over $100, which isn't all that much when you consider that this is a CPU that has been used successfully in space before by NASA.
(I remember a short while ago on an electronics forum there was a discussion about either this or a similar project - can't remember - where someone bet that they were certainly going to fail because they weren't using rad-hard parts. This data point certainly supports that.)