Dale, I just finished crunching my numbers for the year and here is what I found. Being in business only 2 years myself I am still in the heavy advertising part of my career.
I am in 2 phone books. One in a small rural town area and one that goes to several big cities.
The cost to gain a new customer in the big city book with a quarter pg. ad was $164 per customer, I lost $1000 but I gained 44 new customers.
To gain a new customer in the smaller book with a quarter pg. ad was $94. I think I picked up around 30 new customers.
The cost to gain a new customer by mailing postcards to nice middle class areas was $56 per customer, AND the ticket average for the postcard customers was alot higher than the customers I got from the YP, which means I made alot better return on the postcards.
Most advertising you can at least break even on and if you do a good job they will continue to pay off for the years to come.
Next time around I will only be doing small in column ads in the YP, which reminds me, since I switched one book from a quarter pg. down to a small 2" column ad I am actually getting more calls. Go figure! Maybe my picture in the ad was too ugly.
Good luck!