Question about seller fees

I am about to run ads for a kids board game my family created, and educating myself on ppc and sponsored ads. As I calculate ROAS and budgets for ads, I’m noticing how high my seller fees are and wondering if 45% of my selling price is the norm.

I have the game set for 27.75 right now, but probably drop a couple bucks (sells for $25 in brick and mortar) however, it says I have to pay over $12 in various fees. That includes the fba fees.

Is it normal for them to takeover 40%?

If not, is there something I’m doing wrong? I thought maybe I had weight and size dimensions wrong, but those are set up correctly.

If so, it opens a lot of questions about realistic expectations regarding advertising.

I’ve read articles that 8-10% conversion is average, but that sounds extremely high compared to every other ad platform. Is that realistic or a pipe dream?

Lastly, how much of a post do sponsored ads REALLY boost organic sales? Enough to offset if the conversion rate isn’t over 7%?

Caveat; I know there are a ton of variables based on the product sold, but looking to set realistic expectations.