Premiums that rise as your pet ages, the clauses that decide whether a claim pays, and whether self-insuring actually works when the fund doesn't exist yet. The comparison most people never run correctly.
Anything that appears before a policy starts is generally excluded as pre-existing, usually permanently. Some policies count signs that were investigated and never even diagnosed. The window closes quietly, and most people find out afterwards.
Pet premiums typically rise substantially as an animal ages — which is exactly when you'd least want to drop the policy, and when switching is hardest because everything since is now pre-existing.
Lifetime, annual and per-condition cover behave completely differently when a chronic problem appears, and that distinction matters more than the monthly figure. It's also the least understood thing in the category.
A plan to save fifty a month doesn't help with a four-thousand bill in month three. That gap is where most self-insurance plans actually fail, and it's rarely part of the pitch.