It is a fact that the more mainstream you are, the better off you are materially.
For example, Indult priests certainly have a higher standard of living, more pay, and a much more "humane" (and less grueling) work schedule than, say, a Resistance priest.
Of course, a Resistance priest is basically just a Trad priest from the 1970's, or the early days of the Trad movement. Everything was small, disorganized, and in flux; priests and resources were few, etc.
It's simply the way things work. The more personnel you have, the more resources you have, and the larger the organization, the more orderly, regular, and predictable everything becomes. You start getting things like helpers, assistants, and days off. Even vacations are possible!
I know one thing: if I were a mercenary priest, I would be pushing for a deal with Rome too. More recognition and less stigma always translate into more people in the pews. And even though the priests don't get the whole collection, they still can receive gifts from parishioners, eat dinner with them, etc.