Sure, tech gadgets are great and super-useful when things are going well (and I have lots of them, and quite a few from Apple) but when all is said and done, oil powers our society. People need to drive to work no matter how bad the economy gets. I would assume that tech gadgets are the first to go from someone's wish list when the shit hits the fan.
So, even if a tech company has great revenue today, having the sort of P/E ratio Apple has means that it is expected to have that sort of revenue (and revenue growth) for the next couple of decades. While these sorts of P/E ratios maybe make sense for large industrial companies that stick around for half a century or more, do they make sense for tech companies?
1) Their products are usually in the nice-to-have or semi-luxury category, so they don't have as much staying power through downturns*
2) Tech companies are usually outpaced by newer arrivals, so expecting their run to last for decades is a bit optimistic.
* I will agree, however, that Apple has done well during the current downturn we are facing, but that's because it has produced some game-changing devices, like the iPhone, and how often can any company be able to produce game-changing devices?