Hi Flo, I have been on FAA for about 2 and a half years and have had 62 sales of varying amounts, https://fineartamerica.com/profiles/17-paul-thompson?tab=artwork
You add your own mark-up, but they say that they are just a fulfilment centre, and you have to drive your own traffic to your pages and images.
I'm in the UK and almost all have come from America and I didn't send those sellers, so they found me through my descriptions and tags.
Certainly worth the $30 a year, but it has been hard work and intermittent with the sales.
I am also on RB and do much better there.