I think you underestimate the amount of technology and manpower rich countries invest in modern athletes, certainly in the "non-game sports" (things with a start and a finish, plus events such as the long jump or archery, where one competes more against oneself than against the competition, and where the optimal motion sequence can be trained for) and the manpower needed to evaluate measurements.
Fitness and motion analysis are not something they do every few weeks. Endurance athletes have their heart rate measured almost full time, and have lactate measurements taken between set pieces; top sprinters and swimmers have an expert look at video of their starts, turning points, etc. _every training_ so that progress can be tracked and regressions can be caught early; cyclists measure their heart rate and the force they exert on the pedals all the time.
Cameras are cheap nowadays; labor is not. The second athlete may be cheaper than the first, but that curve levels off very quickly. That's why, typically, the big sports have their own training centers, but the smaller sports share infrastructure (if your rowing section has ten persons, sharing infrastructure with canoeists probably is a win; if there are a hundred, that's no longer the case; the canoeists will want slightly different setups for their weight lifting, etc.)
There are ~10,000 athletes going to the Olympics and perhaps 5-10 times as many serious competitors that that did not make the cut for one reason or another. Most of them are not on that kind of a regimen outside of a few national programs or exceptional edge cases.
PS: I have spoken to people in that outer pool from the US it's really dependent on sport and country of origin. But, in the US most people outside of the very top in popular sports have very little backing.
Fitness and motion analysis are not something they do every few weeks. Endurance athletes have their heart rate measured almost full time, and have lactate measurements taken between set pieces; top sprinters and swimmers have an expert look at video of their starts, turning points, etc. _every training_ so that progress can be tracked and regressions can be caught early; cyclists measure their heart rate and the force they exert on the pedals all the time.
Cameras are cheap nowadays; labor is not. The second athlete may be cheaper than the first, but that curve levels off very quickly. That's why, typically, the big sports have their own training centers, but the smaller sports share infrastructure (if your rowing section has ten persons, sharing infrastructure with canoeists probably is a win; if there are a hundred, that's no longer the case; the canoeists will want slightly different setups for their weight lifting, etc.)