There is a threshold in the South Dakota bill for $100k in sales in the state. Small online sellers are not affected
You are also now open to tax audits from all other states, since you may need to prove you are below any exemption limit.
It's a bad deal for small business no matter how you slice it. I think that if your revenue is below ~$100m annually, the future is beginning to look bleak. Very helpful to the big players like Amazon in killing off small competition.
Why wants to win by being the asshole who did it for $500 instead of say a percentage of revenue?
Basic economic principles. You compete by lowering your price. So more competing providers would make it highly likely that price moves closer to cost, because there is a higher chance that one will defect from the current price structure.
To put it plainly. You run a gas station but the guy across the street gets all the customers. You both charge $3 but your cost is only $2. What do you do to get more customers? Lower the price.
I wish I shared that faith in market forces. What seems more likely to the cynic in me is that a big player like PayPal will incorporate it into their merchant services, obtain some overly broad patents on the process, use those to stifle competition, and make the service a nominally cheap add-on (but only for their own customers).