You're totally right but I was asking this question because I wanted to know if there are any other companies similar to Basecamp that pays you SF rates no matter where ever you're in the world.
If you're a freelancer, it's up to you to decide what rate you want, and if you're willing to negotiate on that rate.
For reference, I charge clients about 3x more now, living in a relatively small city in Thailand than I did when I left Melbourne (Australia) several years ago, which is ridiculously more expensive.