I hear ya on the chronic illness, Martha. BTDT ... (and I fear we'll be doing it again in a few years with Senior gal)
At this point, I try to find the best price/hunt for coupons for their cat foods. Did find a cheaper version of the pine pellets I use in their litter boxes, so we'll save some $$ there. At this point, I won't skimp on the vet, especially for senior gal. If $$ got really tight, I'd take the younger ones to the clinic at the humane society for their annual shots.