Some time ago I went back and broke up the goals into smaller brackets. Now each $1000 is another bracket. i.e. 6000-7000, 7000-8000, 8000-9000 etc each have a different revenue per labor hour goal. Those goals are based on numbers we have actually hit in the past but not regularly achieved.
I also increased the portion of the bonus that is tied to this. The GM gets $2.00 per hour and the assistants get $1.00 per hour if they hit it. They get nothing if they miss. For most of the year this amounts to 1/3 of the bonus available. The other 2/3 is tied to smooth operation, cash control, shop cleanliness, food cost etc. All of our bonuses are tied to the number of hours worked and I only pay on regular hours. Overtime is bonus enough!
We do run bigger bonuses when we are busier. Our business cycle has some pretty big swings ($5,000 per week to $25,000 per week). When we are doing 10K per week the manager bonus tends to go up about $1.00 per hour worked to max out at $7. At 15K another dollar. If Christmas week goes well and we are hitting good numbers (Over 20K) he will get $10 per hour worked in bonus and the assistants will get $6.