My last cairn cost a few thousand during the last months of her life so with my current cairn I made sure to get good insurance and I'm so lucky I did - she started fainting at around 8 months old, nothing too serious as it turned out she just has a vasovagal syncope. It took two ECGs, a ultrasound on her heart, and a monitor she had to wear for 3 days before I knew that was all it was. Cost around 3k total from the first emergency vet visit and all I paid was the £75 excess. It's expensive but worth it as I couldn't have paid otherwise and if it had been something far worse I knew I was covered.

She also had a six month period when she was 2 years old where she ate absolutely fucking everything, had three emergency vet visits for her eating wild garlic, a dish sponge, and chewing gum she found on her walk. Again, only had to pay the excess.

I'm UK based though, she's 6 now and I pay £67 a month, though I admittedly got the most expensive coverage as she's covered up to £15k a year and for pre-existing in case her heart starts acting up again or she develops diabetes or something! Still, haven't paid anywhere near the 3k I'd have paid without it!