Settle this for me: how much does it cost to advertise on google?

No fixed price, it's an auction. You set a daily budget and pay per click, and what a click costs depends completely on the industry and area. Some local terms are under a dollar, legal or insurance terms can be 50+. Google can spend up to twice your daily budget on a busy day, but over a month it won't charge more than about 30.4x the daily figure. Most small businesses I've seen start somewhere in the few hundred to a thousand a month range and adjust from there. Search the keyword in Keyword Planner and it shows a bid range, that gives you a rough idea before you spend anything.