Price for Pay per face.

Hi guys. I have my first market gig tomorrow (australia) and have been struggling with how much to charge per face.

Should i be charging one flat rate no matter the design, or have a cheek/eye design price and a more intricate design price?

Is $10Aud for the below designs too much? They may not look worth it to parents as they are not full face... but $5 feels a bit too cheap... what are your thoughts?

What are reasonable price is Aust?

One rule of thumb I have heard is to base your pricing on how much food/water/beer is at the event. I have 3 tiers of pricing and designs are priced on how long they take to paint. Sometimes cheek art takes longer than a quick mask and so it will cost more. Some of my designs have multiple price points. For example, I have a quick Elsa one-stroke design for $5, and mask version for $8, and a more detailed mask for $10. I try to price my designs so that if I have a steady line, I will make >$100 per hour.