The artists make approximately diddly-squat if no one listens to them. Note that they’re not forced into this channel - if they can make a better go of things without it, power to them.
You’re comparing record sales to radio play. Two totally different things, and the former is typically driven by the latter. Also, there is no way indies are making more on physical disc sales, after costs, than they’d make selling the same content digitally.
Tunecore can get a CD made for 1.28 shipped and that is for just 1000 CDs you can get better pricing on larger quantities. iTunes IIRC charges 9.95 for a Digital Album and takes 30% so yeah basic math shows us an Indie can undersell iTunes and still make more money on a physical sale of a CD.