Are enterprise drives really that much more reliable outside of the error recovery timings?
Timings are the primary reason, but the enterprise models usually include some additional sensors to help prevent a physical crash (head smacks platter). Think vibration; it gets to the point a physical crash is imminent, the controller then reduces the rpm (cuts power to the spindle) to bring it's rotational speed, and ultimately the vibration, back down to acceptable limits.
That would be something I brought up before. Many of the proponents of a smaller design suggested it would bring down the cost of the machine, because the price is really driven by the cost of aluminum and building sleds for SATA connections that are paid for either way
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. It is important to consider total costs, but I'm highly skeptical that this would have any effect on the availability of thunderbolt peripherals.
Anything used in a system has an effect on it's overall manufacturing costs.
In this case, the physical enclosure and internal components don't appear to rely much, if at all, on aluminum (not surprised, given the recent increases in the cost for it). So they save some money there. Great. But it's going to be offset by the more expensive silicon (GPU's + CPU) used in this model vs. the budgets allocated for these components in the past.
As per peripherals, that's going to be dictated by how manufacturers/vendors perceive the demand for such products. If they see a massive demand, and can't get the parts, they'll be in contact with the misc. IC suppliers requesting more parts, and in turn, those part makers will do their best to comply as quickly as possible without harming their own companies (damage do to rampant growth or serious QC problems for example). There will be lots of meetings and so on, to be sure of what they think the demand is, and how long it will last, so if it's in their best interest to increase production, they'll do it. If not, they'll see it as a short-term spike, and continue on with existing plans.