It's not really a "slight" career change to switch languages (especially if you're transferring to a new company) though there seems to be an unfortunate trope that it's quite trivial.
The effort involved also depends on framework, business knowledge, stack side and a whole lot of other factors, it's not always (or often?) the case you're just swapping in one language for another, and even this latter "simple" case is often a significant undertaking.
That doesn't mean you've got to drop a rank, but it does mean you have to be prepared for the possibility or be able to explain what exactly you are bringing to the table that justifies the money over a competitor applicant who can hit the ground running.
Or learn the new language in your own time and contribute to open source to establish competence you can demonstrate if you don't have the opportunity on the job.
The effort involved also depends on framework, business knowledge, stack side and a whole lot of other factors, it's not always (or often?) the case you're just swapping in one language for another, and even this latter "simple" case is often a significant undertaking.
That doesn't mean you've got to drop a rank, but it does mean you have to be prepared for the possibility or be able to explain what exactly you are bringing to the table that justifies the money over a competitor applicant who can hit the ground running.
Or learn the new language in your own time and contribute to open source to establish competence you can demonstrate if you don't have the opportunity on the job.