That's a strange way to design a financial contract system. I mean, just like Rust checks for memory safety at compile time, can't the contract language make similar checks? Or perhaps the contracts can run in a simulator first?

Yes, you can write a contract language (or improve an existing one) which contains static checks. That hasn't been implemented yet probably because of lack of resources. The higher level contract language is compiled down to byte code.

You can in addition implement these safety checks to be executed during runtime, but that costs money.

It's not a financial contract system. It's a decentralized general purpose computing platform. It can be used for financial contracts.