If you don't charge by the hour, you can make money dealing with an Avalera-like installation. You create a proposal for ""Streamlined Sales Tax System"" with 3 deliverable options in it. The lowest price is where you point them at Avalera and offer ~2 analysis virtual meetings with the customer to review what they found and where they want to go, and leave it to them. The highest one includes the discovery and analysis, and installation/configuratoin and training and support. The middle one is less turnkey but you are along their ride to give them confidence. How much is it worth to them for peace of mind that the whole %^&* process will work? That's what you price the highest at.
I've found that when you break ""an upgrade"" into its pieces, most of them want way more than just the software install/conversion. But they didn't know that the added education, coaching, etc. doesn't have to be part of the ""upgrade"". When you give them the choice, they'll almost always pay for the added service. Just don't bill it hourly!!