The trouble is that veterinary medicine has come on leaps and bounds in recent years. In the past, a cruciate ligament was repaired by a suture that was designed to take the strain of the ruptured ligament, but would sometimes rupture later in life, or not quite give perfect recovery. Nowadays, there are several options (including the suture method for certain circumstances including lack of funds) and several options that involve delicate precise cutting and plating of the bone, which have better chance of returning to normal function and longevity, however, tend to come at a greater cost, due to equipment and the further training required to perform the surgery. This is expressed in the cost - and it's not just cruciates, there are a number of surgeries or medical treatments that are much better now than in the past, but may cost more.
I believe a lot of the problem with the perception of veterinary costs is related to having a National Health Service. Because it costs us nothing when we go to the doctor, it is easy to overlook how much it actually costs to take a blood sample, perform a surgery, bandage a wound. Look up online the comparison between an American who compared the hospital breakdown of his cruciate repair with that of his dog - very similar operation, very different costs, and although £2500 seems like an absolute fortune for a dog surgery, when you look at what it costs for a human, it suddenly seems extremely good value for money.
I would highly recommend people insure their animals, because it may well be that you never need it, but if you are putting in a set amount per month, and know your excess for each condition is a set amount that you will be able to pay for, then however many times you have an emergency operation for swallowing something, or have an animal hit by a car, or start up with long term medication for a lifelong disease, you know the amount you pay per month plus a one off excess will cover it. If you can manage to find £7500 in a month when you have a major surgery that has complications, or can put it away in savings, but are prepared for vet bills that may still happen once the savings account is empty, then do so.
As a vet, it is heartbreaking to not be able to do the best for an animal because people can't afford it, and insurance usually means that they can.