Why are extended warranties for tape auto loaders so high (nearly 50% the cost of the drive)?

Besides the implied level of support and warranty of tape changes being "enterprise" products, they're actually fairly complicated devices.

Tape changer robots have a reasonably hard job. They're robots. They have acutators and sensors, tight tolerances, and other robot-y things. Generally speaking, you want them to be reliable, so it costs money in R&D, which gets amortized over the costs of the units and their extended warranties.

It signifies that tape drives are a consumable resource. For the same reason you couldn't even buy an extended warranty on an "enterprise SATA" drive 3 years ago, they just fail after a certain amount of usage. Tape drives are mechanical devices. The tape-heads wear out over time from simple use. The extended warranty is just their estimate at the likelihood that you'll wear out your tape-heads in the warranty period.

When it comes to auto-loaders, you also have a bunch of robotics inside. With that many actually moving parts, the warranty has to cost more than a server that sits there and spins fans while shuffling bits around.

Moving parts...dirt...wear...you'll pay it because you'll be in a panic when you need the tape drive working and it's usually discovered right when a server dies...high cost to get the replacement to you right away, maybe?

Probably because they know you'll pay it for high end equipment and businesses want peace of mind knowing there's someone to scream at and be responsible for the blame.

Its like insurance - if its more likely to happen (ie break more often from a complicated set of moving parts), going to cost a lot to fix (replacement or sending a tech out, again lots of parts requires lots of training), and has a relatively high likelihood of being used in the event it is necessary (enterprises dont just let their backup systems fall apart and not worry about it), its going to cost more.