It’s very easy to spot liquid damage, as many devices have indicators inside if liquid reaches them. That’s exactly what happened when D’s laptop got wet (we think it happened in the plane).
We took it to an Apple Store, and they saw the problem right away when they opened the case. It would have cost $700 to replace the motherboard, and I found we could get a brand-new laptop with better specs for about $300 more. We opted for the new laptop, so the minimum spend for restoring just one device to functionality would have been $700 at a minimum.
For the low price I paid for the policy I just purchased, where this kind of damage is expressly covered, along with a host of other things, it’s definitely worth the peace of mind.