What were common benefits from marriage alliances, apart from alliance in case of war? Toll freedom?

As we might expect from a society which is more than 90% agricultural in its economy, the major benefit was:

Joking aside, marriages were a key method of acquiring, expanding, and rationalizing estates, from the lowliest peasant who had to get permission to marry to kings and queens. After all, you didn’t have a free market in land so marriage was one of the few times in which you could actually transfer property, and since nobles couldn’t work for a living, marrying well was one of the few things they could do to become economically self-sufficient.