The burgers weren't your basic hamburgers. I got 97% lean ultra-beef, ground chicken breast and ground turkey breast, and mixed them all together with spices. What I ended up with was pretty low-fat, which actually makes grilling more difficult. And the flavor wasn't really what I was looking for, but I think it would make for excellent meat loaf. I ended up using most of the burgers as additives to various food dishes rather than as straight burgers. Worked really well in soup/stew.
I think the fat content and texture could easily be made up with some canola or olive oil, probably a teaspoon per pound at the most. I don't know if it would work well for grilling: the chicken has a lot of moisture and not good cohesion. A better mix would be 50/50 ultra-lean ground beef and ground turkey breast.
I do pay a premium for the ultra-lean beef. At the same time, I'm eating less. Net result is savings. And a little teriyaki mixed in provides some seriously good flavor.
I've also rediscovered oatmeal as a filler. Most recently in chicken soup.