House Tremere, unlike your covenant, has copies of the best available Roots for every Art (they traded the use of their junior magi for them), along with several Branches that they managed to get off of Durenmar. In fact, they probably copy said Branches internally at Coeris - while they don't sell copies of said Branches, they do make them available to more Tremere magi than they would be at Durenmar (which has an unofficial policy of not actually making their good books available). They pay handsomely for a library of quality tractati. No Tremere magus should have to study from vis.
House Tremere has longevity specialists on contract. (No, this isn't specifically on the list of available gifts, but come on.) When a Tremere magus turns 35, they can be assured that their exarch has already marked them on one such specialist's calendar and that their LR is paid for.
Coeris has a bigger stockpile of magic items than anywhere except Verdi, tailored to a variety of uses. Need one? Just sign for it. (Youngsters, expect to wait a bit.)
In short, House Tremere is a lot closer to that ideal Order that works together and shares resources for the good of all than...well, the regular Order is. I would assume that Tremere magi can count on decent compensation for the season they spend in service to the House.