I hear you.
A lot can be said about the move from free to free/token-based approach.
100USD/4 days is rather on the lower side IMO. Sometimes I burn over 50 EUR on a single day without doing crazy stuff. So cost is definitely a factor here.
Being able to choose a model would indeed be awesome. My feeling is that this will be added in the future, especially since 'using an open source model is good enough' becomes more and more popular. But that is just my feeling, can't add any facts.
I suggest you set up the alerts for genie usage which can be found in the docs (.https://docs.databricks.com/aws/en/genie/budgets).
Also with a query on the system.billing tables can give you the LLM spent.
But all this is not realtime. it takes a while before the actual spent is stored so you might still be surprised the next day.
Perhaps others have additional methods. Would be nice to see them all as cost control is pretty important.