I do, but at this point I have spent enough on insurance to have lost a scope and never used it.
You'll most likely come out better self-insuring. That's how insurance works.
You are correct on that.
However...
I almost Never see anyone actually setting that money they save on insurance aside to cover the losses when something big does get lost.
We deal with resellers all the time that want us to ship on their own UPS / FedEx or such accounts and demand that we don't insure it because they have their own insurance cover or have a 3rd party insurance. We flatly refuse because in a quarter century of doing shipping to resellers, we have never once had a reseller that claimed "their own insurance," actually honestly just accept it if the carrier lost or damaged the item being shipped to them.
EVERY single time they demanded we make it right on their cost or they would make false claims to their bank or credit card company for fraud etc.
They get amazingly creative about it.
Also we have found that resellers were using that also as their excuse when they shipped it from their end to another customer without insurance and it got damaged, or they dropped / damaged things in house, trying to claim that it was damaged in shipping. (Usually busted when we ask for a picture of the shipping box and they say something like, "our policy is to destroy all the boxes immediately", right.
So the long and short is, YES self insuring will save you lots of money over the long run.
However that means you actually have to set aside funds to cover the event because it WILL eventually happen no matter what carrier you use.
And NEVER trust someone else claiming that they don't need to pay for insurance because they will take care of it.