To be honest I bid on this just to make a point.
I don't think you realise how many hours it takes to make a complete song. Asking to pay 20$ is frankly insulting.
A fully fledged 3 minute song can take anything between 20 and 40 hours of work from conception to final product -
Composition, lyrics, recording and performance, mixing, mastering.
Even 150$ is unrealistically low - the going rate is about 200-300$ a minute of music.