Say you list a table lamp on your website at $100, tax included. Well, if you sell that table lamp to a buyer in Connecticut (where the tax rate is a flat 6.35%) then you’re required to remit $6.35 in sales tax to the state of Connecticut on that transaction.

But if you sell the same table lamp to a buyer in Aberdeen, Washington, where the sales tax rate is 9.08%, then you’d be required to remit $9.08 in sales tax to the state of Washington.

As you can see, you are cutting into your profit margin by including tax in your pricing.

Further, US customers are accustomed to paying their local sales tax rates. We’re so accustomed to paying odd amounts in sales tax that paying a flat rate might surprise us or leave us a little confused.

This is anti-consumer bullshit nonsense. All they did was hid their only real "con" behind a wall of text. "As you can see, you are cutting into your profit margin by including sales tax"

And the last paragraph is fucking stupid too. People are too used to seeing numbers, so other numbers will confuse them!