I build and sell amazon aff sites. I have sold sites to FE International, Empireflippers. What your screenshot shows is "Amazon FBA" not Amazon Affiliate site.
For an Amazon affiliate site, if one site has an avg. net profit (income after the expenses) of at least $500 for the last six months, it can be sold at 24x-32x multiple.
For example, if one site makes $1000 of net profit for the last six month on an avg, it can be sold at $24k-32k.
Mostly selling price depends on how well the site is built and future potential. If it was built with a white hat strategy, the price could be higher, if your site has pbn, the price could be lower (that's not always the case).
It really depends on how much one site can be sold for and people do flip sites at this rate.