The problem is not just that Rust takes a few seconds longer once. It compounds across the edit/debug cycle. If you make around 800 save/check iterations in a day, then a 2.5–3.5s feedback loop costs roughly 34–48 minutes of waiting per day. The same number of iterations at 200ms costs about 2.8 minutes.
So the practical delta is around half an hour to three quarters of an hour per day, or multiple hours per week. That directly affects flow state and experimentation speed. over the span of a month that's 2 full days worth of work waiting for the compiler. Or if you take my company's evaluation of the average engineer's hour cost it's roughly 2550 per month or almost 30k per year, obviously it's a bit exaggerated, you don't spend a full year refactoring and working like that, but even a tenth of that is still a big lump of money if you scale it to a few teams.
Now it needs to be taken with a huge pinch of salts because Rust provides other benefits that offsets the fact that it's painfully slow to compile, but still worth noting
