How much do tech brands spend on online advertising? any ideas and who spends the most?

Certainly B2B brands spend more, because the ROI on customer acquisition is much easier to measure and offers a near immediate return.

Another distinction surrounding spending more/less, all competition and budgets aside, is if the product or service is already being searched for.

If you have an inbound offering, you don't need to do as much traditional "advertising" with the advent of SEO, press, etc. But if you invent something brand new, a lot of your advertising $$ goes to simply educating consumers about a) who you are and b) what you do.