You are seeing the retail price. The price schools get through vendors are much lower. Sure, you can find laptops used on eBay and reformat them as needed. That's a terrible way to run a school's IT department with modern 1 Chromebook per child policies.
You couldn't reliably source enough cheap laptops to endlessly have to work on them to get them provisioned for students while also repairing the 2-3 broken Chromebooks per week because kids are hard on them.
Volume discount Chromebooks are the de facto way schools run because they can basically get them at cost. The only profit is when people pay retail prices, which as you pointed out is not a reasonable price for the pure performance of the hardware. But again, they are really designed for schools by definition so they are very limited and can't do much general computing. As a result they do not need performance parity with anything but ChromeOS and any web apps that might get installed.
The final thing I'd like to point out is that we have been gaining less raw performance in CPUs each year and moving toward better performance per watt instead. Laptops especially don't need huge, hot, power hungry CPUs anymore. So instead of making them faster and faster for minimal end-user benefit they chose to make battery life the priority because that really does give much more benefit to the end user.
Most devices are now aimed at media consumption rather than more power hungry media creation. We've reached "good enough" performance that the N100 can consume YouTube videos and run web apps while still having a battery that lasts all day (or close). That's all schools need for a basic computing device.
You seem like a power user who needs more than a basic computing device. The Chromebook is not designed for your needs :)