The funny thing is, they are making more money than that on the collected taxes.
Back when no one was collecting taxes on line, I helped create a .com business in anticipation of eventual mandatory collection. I addition to fees paid by sellers for hassle free tax services, there were two other money makers:
- States provide discounts to tax 'bundlers' that collect tax across jurisdiction & sellers. In some states and conditions, this could be 10%.
- Filings could be monthly or quarterly, so they get the float on holding the seller's taxes. Granted, not huge, but it adds up.
We got a lot of interest, but not enough funding to continue. No one new how soon it would be before the service was needed. It took about 20 years to get there, so I guess they were right.