Nearly 20% of Amazon merchants make more than $1m in sales per year

"A survey found that 19 percent of third-party merchants that sell goods on Amazon have made more than $1 million in sales this year, an increase from 10 percent in 2017. It also found that 3 percent made more than $10 million, an increase of 1 percent from last year.
Feedvisor, an eCommerce company that helps merchants price goods on Amazon and other online marketplaces, surveyed 1,200 Amazon merchants this year and 1,600 in 2017, and was distributed to the same sellers both years. Nearly 50 percent of the merchants surveyed sell almost exclusively with Amazon, with revenue from the eCommerce marketplace accounting for 81 percent to 100 percent of their sales."

Source:  PYMNTS, 24th May 2018