You probably want "-f bestaudio" instead of "--extract-audio". The former will download just the audio and skip the video which is significantly faster (and cheaper when on a metered connection). However you will have to do the conversion to MP3 yourself afterwards (e.g. with ffmpeg) if you want that format specifically.
These days, with AAC being supported pretty much everywhere you're probably better off just using the " -f 140" option to get the 128kbps m4a file, which at least saves the further (albeit subtle) degradation caused by another lossy to lossy transcode.
However, I'll never forget things like "tar -zxvf", "ffmpeg -i vid.mp4 image-%04d.png" and "convert image-*.png +dither anim.gif".