If it produces a benefit, that cost is trivial for any business with a reasonable amount of sales.

1% boost in conversion in a business with $100,000 annual sales = $1000, which is almost double the price of the lowest plan.

Yes. In fact we have an agency account which costs a bit more. We use it all the time for a roster of folks who don't want to pay the monthly fee but are interested in improving conversion rates.

Its not an artifact that's intuitive to me either, but the numbers shown that good landing pages drive conversions.