I know what you mean about the price per use and I really agonized (a long time ago) about spending the money for the specialty tool. However, my price per use & the part and finger damage avoided over the years has been worth it. I use the model 22 which is advertized to fit "all strain relief bushings for chassis ports up to 7/8". I have never needed a different size tool. It is "adjustable" in the sense that you can remove the pivot screw and move the jaw position on the gear. I have done that when I used it for very large or very small strain relief bushings. Hardly ever need to do that though. I wouldn't want to be without the tool now.
As I understand it the model 30 is a heavy duty version of the model 22 but it fits the same range of parts. The 22 has been adequate for my use. One supplier's info with photo is at the link below .
Heyco - 0022 - Strain Relief Bushing Pliers