It would probably have been more accurate to say that they can't check everything at their current price points. With enough money, everything (or practically everything) could be checked.
I work for a company in the chip making business. Making chips is a very complex and involved process, and requires generally more stringent quality control than building trailers or motorhomes, if only because smaller errors/faults will cause significant problems. Outgoing quality levels for chips (once through production and testing) are measured in DPM -- defective parts per million, somewhere in the low 100's range I think for typical consumer-level chips. (I may be off on that; I'm a couple steps removed from such details.) That doesn't mean that the production line makes 99.99% good chips, not by a long shot; but through thorough automated testing, the bad ones are virtually all screened out.
Exactly how much time (and hence money) is spent on testing and verification depends to a large extent on the value of the chip and of the device it goes into. A chip destined for a satellite, for instance, where repair or replacement in outer space would cost billions, will receive far more testing and verification than one that goes into a $10 wristwatch.
If RV buyers demanded (and were willing to pay for) consistent quality, I suspect the builders would be able to achieve that...after a lot of (possibly painful) work.