You can't generate 10k LOC in a day with a coding agent either, not if you want to actually understand it and review it (which you must do if you don't want the quality of your work to go into the toilet).

> Can you write 10k LOC a day without a coding agent?

Easily, by writing a code generator. Or disassemble a 1k C program.

> They just allow things that wouldn't be economically possible without them.

It’s not economical to have more code. It’s economical to have correct code and the way to do that is with the power of abstraction. Instead of dealings with opcodes, you have assemblers and macros. Then it’s C, next it’s python, and what would have been a 10k program is now just a few lines.