Avalara is expensive. It works out to being cheaper if you have sufficient scale, but it's generally pricier for small businesses.

However, that is because you're paying for their customer support, and Avalara customer support is very good. Every issue we've had has been dealt with promptly, including issues where Avalara misfiled a return. (Long story short: they owned up to the mistake and corrected it with the state without any additional cost or penalties to us.)