With the $10 plan, it's 1 cent per a search for the first thousand, and maybe a thousand searches a month doesn't sound like a whole lot but supposedly the average user on Google does 3 to 4 searches a day (who knows what the actual source for that is). Thought in that case the $5 plan would be better.

Google doesn't seem to provide a dashboard which summarizes how many searches one has done personally over a period of time, though it does list them all on https://myactivity.google.com/product/search if you haven't opted out.

Most browsers also provide an easy way to switch between search engines, though personally I would suggest always using Kagi if you're going to spend the money, because some of the of value comes from generally having better results, in addition to being able to filter out SEO garbage for specific search topics (like programming queries).

Also, to be fair, Kagi is not perfect. Google's calculator and unit converter are better in my experience, for example. And I still use Google at work (software dev) because I refuse to use personal accounts on work devices, but even then I find myself using my phone sometimes to search Kagi when Google is not turning anything up.

However, I've watched Google's search quality drop for a long while now, and I like what Kagi is doing, so I support them.

P.S. If you're worried about unlimited spend, Kagi provides settings to cap pay-as-you-go costs.