How much do keywords cost on google - what's the honest answer?

Honest answer is it depends completely on the keyword. You don't buy a keyword at a set price, you bid in an auction every time someone searches, and you pay per click. Some niches are well under a dollar a click, things like legal or insurance can be many times that. Google Ads has a free Keyword Planner that gives estimated bid ranges for your area. Use that, and set a daily budget so you can't overspend while you learn.