author here. I agree with what you're saying in broad terms. And yes, you're right that handling sales tax perfectly at launch won't kill your product.

What's the killer is all of the work _surrounding_ that small task.

Actually charging sales tax didn't long. More or less

if address.region in TAXABLE_REGIONS: subscription.sync()

What took the longest was developing and deciding how the screens surrounding will work. Answering things like:

- Which fields do we want to capture for an address? - How do we want to store states (or provinces, or prefectures) in a standardized way? - Is there a library that will let me select countries and prefectures? (Answer yes, pycountry is pretty great) - How do I integrate this library into my backend / front end?

In my mind it's just fit and finish. Like making the motherboard and inside of the case as beautiful as the outside. If I try and half-ass it or skip it, I'm just going to have to double back and make it right.

I do appreciate your final sentence. I'll keep that in mind going forward. :-)