whats the point of Stipe Tax anyway? they solve only the trivial part (calculating how much VAT is due for a transaction), while ignoring the hard part (actually paying the VAT to hundreds of tax offices in countries all around the world). despite only solving the trivial part that any developer can do in a day, they take another huge chunk of your revenue. seems like a bad deal.
Calculation is trivial if you are only operating in a single tax jurisdiction, maybe.
Tax calculation software handles all the different tax rates for product categories your business sells, changes in city/district/federal tax rates, brackets and min/max caps, sales tax holidays, etc. It costs money to maintain those databases.
Saying it can be done by any developer in a day is absurd.