Right! It costs millions to certify something for flight even if it's been in commercial use for years. Even for something as simple as swapping a spinning disk for an SSD. And it has to be verified in-situ with the other components of the system. And separate testing and documentation is required for each airframe variant ("Type certificate"), so a swap for a 747 and 737 even though they're both Boeing products requires separate testing and documentation. There could be THOUSANDS of pages of documentation for a non-trivial product.