Commissions really do vary, of course. Depending if you want sketches to full body and backgrounds with color.

Dry, really rough sketches like these are $15-$25+ depending on how many sketches you want of a character (just the ones on the left)-http://yuroboros.deviantart.com/art.....work-426016083

If you are wanting a sketch page of a single character it's $50 -http://yuroboros.deviantart.com/art.....2550&qo=12

Multiple characters adds $15 to the sketch page so all together it's $65-http://www.furaffinity.net/view/14882053/

Speed paint sketches vary from $20-$30+ depending on how colored you want it-https://40.media.tumblr.com/6e0458e.....amu8o1_540.png https://41.media.tumblr.com/d4e7e55.....amu8o1_540.png

Refined sketches with a single color are $30-Sketch Commission Sketch Commission-http://yuroboros.deviantart.com/art.....-Ahk-384829423
Bust + full body sketch w/ semi color are $35-$45-http://yuroboros.deviantart.com/art.....sion-337627030

Bust with color is $25-35 depending on how complex the character is-http://yuroboros.deviantart.com/art.....comm-458245848

Full body w/ color $40-http://yuroboros.deviantart.com/art.....-ref-452643204

Full body + Bust both with color is $50+-http://yuroboros.deviantart.com/art.....Croc-473504542

Reference sheets really vary normally they are $85+-http://yuroboros.deviantart.com/art.....-WIP-446436782 http://yuroboros.deviantart.com/art.....2550&qo=17

Full background w a character is $130+-http://yuroboros.deviantart.com/art.....nata-272285818
http://yuroboros.deviantart.com/art.....-E-N-387900279 http://yuroboros.deviantart.com/art.....62550&qo=4

Multiple Characters have an added $10 per character- http://yuroboros.deviantart.com/art.....62550&qo=1