Durable

I may agree with you just a little. The physical cost of the additional components is not extremely high. But there is some additional cost and extra markup on top of that is a good business decision.

There is extra stuff in there that costs more money.

Part of that extra stuff is the shock protection for the interior. You don't want capacitors falling off the board surface, for example. Cheap stuff does this by covering everything in epoxy but that makes it effectively unservicable. I don't actually know what the Panasonic Toughbook does for this problem.

There is also a fancy shock cushion for the hard drive or replacing the drive with an SSD. Either option costs more than standard.

Two things that justify extra markup is rarity and testing.

Because there is some increased cost associated with toughness, fewer customers will buy the product so the price must be even higher to compensate for fewer sales. Those customers that will buy it are looking for tough durability specifically and so the price may be higher because its a hard to find quality.

Testing for toughness means even more destructive tests on samples. I doubt you see Sony dropping many Vaio laptops onto concrete floors. But if toughness is one of your primary selling points, you will want to make sure your product is staying tough by testing a few out of every thousand.