for those who sell prints of their work

It depends on the size. For Lettersize I usually use our own printer who prints without a white edge.
For double lettersize I used to go to a printshop.
Big prints I print on my A2 printer (4x lettersize) that I got for free from school trash.

Basically its good to think first how many prints you wish to make. If you make a limited edition you can ask a lot for a print. For example, I ask 50$ for my A2 prints with a limit of under 5.
That also pays off to have them printed on really fine paper or professionally (expect it to cost more)
For my more “mainstream pieces” in more mainstream sizes I made simple prints on thick paper. But I also dont sell them for that much.
You kind of have to find your own balance with the prints, I for example found that people were willing to invest more if they knew its a poster and its 1 of 3.
People love portfolios in lettersize, especially if they are mixed (bw and color). People love the little poster prints (double lettersize) even if they have a white boarder and are basically just “better laserprints”. People dont like my lettersize prints, even if they cost only 4-5$. Bookmarks cost 3 $ and they buy them in a heartbeat.
My hint is: start small. Invest into material cost out of your winnings, and if you start see that you keep it in a reasonable price level. You really dont want to end up having spent a lot of money and having tons of prints of your own artwork.
Especially if you sell it online, you can still reprint the next day/week. Its different if you go to exhibits.

Deviantart offers a print system, if you want to try. You offer the works for print and people order it themselves, deviant ships it and the stuff. You will get lesser pay than if you do it yourself, but also less fuss. I dont know yet how it is with the Deviant Dollar, how you get paid your part eventually. I recall reading about you using the DeviantDollar to buy stuff on Devi, but I’m not sure if that still applies.
Hope this helps 🙂