They simply won't make the effort. Quantify your successes. If you can, give numbers. Say so, and give numbers to back it up. If you don't want to give exact dollars, give the percent of budget you saved.
Nothing makes a stronger case than a hard number.
Whenever possible, show pictures of past work. In color, if you can. It may be hard to show pictures of a some types of projects, but you should find a way to do it anyway. Pictures are eye-catching and they compel the reader to read the text. Also, use tables to summarize the elements of the past projects, the similarities to the proposed project, and the benefits you'll bring.