There are other factors. Valuations in tech now depend on our current regulatory and financial environment:
1- Absolutely no real privacy regulation exists in the US, where people's information can be bought and sold freely. (I know there is regulation, but not real regulatory activity means it's de-facto unregulated)
2- There's no anti-trust activity and companies like microsoft, google and facebook can engage in anti-competitive behaviors of all types: buying competitors and closing them to reduce competition (it seems the case with Wunderlist), operate a market and be a participant in it while undermining other market participants using inside information, create a monopoly or oligopoly with no real regulatory costs (aside from a small % of earnings being taxed as 'fines'), actively conspiring to avoid competition for employee salaries, etc
3- Very low interest rates/net negative interest rates for capital holders with opaque and byzantine distribution of newly minted fiat.
4- Zero consequences for undermining democratic institutions by creating revolving doors between regulatory agencies and the companies they are supposed to regulate.
5- Regressive regulatory compliance costs
While the ones who benefit from such an environment would like to make it seem this is the natural state of the economy, it isn't, it's a very new and very strange experiment.
Also, while capital holders would like people to think that the current state of prosperity is caused by our current system of regulatory and financial application, these same people then agree that the greatest advancement in standards of living for the western world happened during the 1920-1960s, a time when the regulatory and financial systems were very different (like a 90% tax on earnings above $50 mill/year (in 2019 money)). So I'd guess we could advance just as well if not better with something more akin to what was then.
I'm hoping our current conditions will not remain over the next 40+ years and some of these valuations will be more in line with traditional P/E ratios.
Anyone can make a chat app. Making a chat app with 100M+ users takes years of effort and luck.