Welcome to FDMB.
To reduce costs, many of us use human glucometers with feline-speecific reference numbers as described in my signature link Glucometer Notes. This reduces going to the vet for curves and tests for fructosamine.
Another method is to feed an over the counter, low carb, canned or raw food instead of pricey prescription food which has no better ingredients, just a higher price. I feed Friskies pates, mainly Turkey and Giblet or Poultry Platter.