Honestly, I couldn't tell you that for my company. My wife tracks the financials since she is the accountant. I can tell you what makes the best returns for me.
Magnetic business cards
Advertising in the service directory of local papers.
Newsletters
The magnetic cards cost about 13 cents each but it has increased our repeat business 60%.
Service directory advertising costs me about 2,500 a month but brings in sales on average of 8-10,000 a week.
Newsletters cost very little the way I do them and they can be used to kick up business during the times when things may slow down.
(my company works all year round) providing various services, not just power washing.
I'd guess my monthly advertising budget is around 3,000 a month with gross sales resulting in enough money to cover it and have pretty much everything I want. (except that 50" flat screen plasma tv I've been looking at) <G>