The coupon at the bottom says that your prices are subject to haggling. Do you really want to let price be a sales tool?
I'm not saying yay or nay, just think about it. It's difficult to convince customers that your quality is top notch and then turn around and give discounts. I've always felt that discounts are for the guys who don't really have confidence in their work.
On the other hand, if you do really good work, ask to get paid for it. Make your quality the sales tool and not the price. I think that if you leave the coupon off, you'll get just as many calls as if you put the coupon on. But the quality of the customers that call will be higher.