hugeblack, this is just one way to preserve your seed/private keys from fire, water or any other external influence. But there is no way to engrave seed in this or any other metal plate, and that it is not visible to you or thief. This kind of backup requires that owner is find best hidden place and store such plate there.
Regarding price, Titanium is relatively expensive material because of its excellent features and because it is friendly to humans and nature. If you buy such plates you can be sure it will last very long time.
https://www.nssmc.com/en/product/titan/feature/