Artists can disable full-length previews if this is a concern. Otherwise, I don't think Bandcamp's 320kbps MP3s are any more attractive than a YouTube rip.

Previews/free streaming on bandcamp is 128 kbps mp3 only. If you buy music there, you get the whole spread, lossy and lossless, mp3 320/v0, aac, ogg, flac, even wav. (Only thing notably missing at this point is opus, which would be fantastic to have, like for example, opus at 64k (space saving/space efficient) and 256k (quality), although vorbis or aac at whatever quality they have it set to is pretty good as a space efficient option)