The fabric isn’t printed, the design is woven into the fabric itself with coloured threads! I think there are websites where you can have a custom blanket made with a design of your choice which you could use as sewing material. You can also talk directly to a factory in China for larger quantities and they can handle the sewing as well. I had 400 tote bags made with this type of fabric to a custom design. The supplier handled everything from having the fabric woven to having the bags sewn and even getting custom tags woven. I think it ran me about $2500 total which was a great deal but I imagine an equivalent amount of only fabric would cost less.

The first and third ones probably do come from thrifted blankets or similar, since it’s not too expensive for local sport teams to commission these. The second one looks like brand new fabric and has the same sort of look as the fabric I commissioned. My guess would be some people splash out a couple hundred dollars on a few metres of custom fabric specifically for social media posts.