Catering and Tipping

I contacted my caterer and asked if tips were included in the server estimate. She replied:

" We do not include a tip in your proposal. Tipping is not expected, but of course appreciated and it's entirely up to you"

Are catering staff paid more reasonably than waiters? If so, what sort of tip should I give based on these expenses:

Menu 3,625.00
Beverages 350.00
Staffing 2,058.00
Equipment 1,850.00
Damage Waiver Fee 44.00
Sales Tax - VA (5%) 396.25
Delivery, Pick-Up and Trash Removal 100.0

Edit: My question is not 'what to tip waiters', I want to know if- due to the itemized 'staffing' section etc, on my invoice, and the caterers reply- if it seems that the serving staff is likely to be paid a living wage or the sub-standard waiters wage.

P.S.: 7 staff. Includes 1 supervisor/server, 1 chef, 1 pantry assistant, 3 servers and 1 bartender to begin arriving at 3:00pm and departing at 10:30pm. Averages to $42/ea an hour.