I once checked a clear plastic umbrella that cost $5 on Delta Shuttle. It arrived undamaged.
Anyway, there two ways to improve your success rates.
1) Check a cap gun/starter pistol inside a giant hard plastic case with multiple slide-locking latches. Provide your own high-quality locks (not 3-seconds to pick Master). This approach makes it too difficult for most to steal, and since it's a "gun", it will raise suspicion if it goes missing.
2) Don't check a $500+ bag that likely holds $1000+ in items. $500 is better lets toss this sucker and see how it survives! Check a no-name junker over and over until it splits at the seams and replace it. Don't lock it, don't bother with the paperwork. In fact don't lock your $500 bag either, a bic pen can open it and there's probably thousands of "TSA keys" that go missing anyway.