Well, according to Microsoft:
"It's estimated that developers create 70 bugs per 1,000 lines of code and that fixing a bug takes 30 times longer than writing a line of code,..."
Which is kind of inline with other estimates.
Let's stick a finger in the air and assume only half of those bugs are sloppy use of memory that using Rust would prevent. After all you have tests in place for logic errors, right? So that is 15 time longer to fix than write.
I conclude that if the limit to your rate your production is the compile time, then a compiler cam be 15 times slower than what you are used to and you are still breaking even in productivity overall.
On a slightly different tack, perhaps ones productivity should not be limited by compile time. If one understood ones problem (and solution) well and if one understood ones programming language well then waiting for a compiler should only be a small percentage of your time.
Consider a mathematician creating a 100 page proof of some theorem he has come up with. Typically he cannot compile that to check for correctness. He has to understand what he is writing and check it very carefully before publishing.