There's no cutoff for artist pages, Mike. I have over 5K followers. Over the past few years I have put links to my FB page wherever I can, and I have a sign and QR code that lets people follow me right from the brick and mortar gallery I show in. I get about 10-25 new followers a week on average. Sometimes I get a flurry and will get dozens in a week, I assume that's from someone influential sharing something.
These days it will be difficult to gain a significant amount of followers without some targeted effort (like an ad, or having someone with a ton of connections promote you, or having a post go viral) You can't just expect your current set of followers to grow on it's own anymore. Ask your followers to share your content. Give them something to share (I give away correctly sized and discreetly labeled Facebook banners that my followers can use and share).
These days, posts reach about 10% of your total audience. When I don't boost a post, it gets in front of about 575 of my followers. I get good post engagement and have messages from my followers with questions and comments daily. I try to post a few times a week, and I try to offer interesting content; new images of mine, links to interesting art news, new products (shower curtains and duvets most recently). Another noteworthy stat is I get about 10-20% clickthrough, which means of the 575 who saw the post, about 50-100 people click on it.
I have boosted posts a couple of times, both times for a specific product featuring my best selling images. Both times I have seen an increase in sales and made back my boost budget more than 15x over. Lots of folks here don't believe in paying to play, but it works for me. I would only do it and expect results with images that are proven sellers, though.