The test equipment is hundreds of thousands of dollars each and everything used for PCIe3 doesn't have the bandwidth to go to PCIe 4. The bigger companies have no problem scaling up but for smaller players it's a serious consideration. Even at satellite offices of larger companies, it can be difficult to get the capital outlay for your lab to buy something like a BERT. We're talking millions of dollars at scale. Fortunately, most of the equipment that works for PCIe4 will also work for PCIe5.