Mixing:

$15 per track/instrument.

Example: 1. vocal 2.back vocal 3. piano 4. synth 5. bass 6. kick 7. snare 8 hihat 9. clap 10. tom

these are 10 tracks/instruments. 10 X 15 = $150

Mastering:

$100 per song.

$250 multitrack mastering per song.

Example: Stereo mixed vocals, Stereo mixed instruments, Stereo mixed drums

these are three stereo tracks, could be more, could be less.