Musicalmrsc, a lot of this sounds familiar (in my life I mean). Maybe you need to cut some of these conversations short. Maybe a “no, sorry,” for example with researching products, services, and quotes, and with the lawn mower.
First you need to be completely clear in your own mind that you don’t want to do it. Then decide a polite way of saying it, and stand your ground. Smile, shrug, hug, and/or change the subject. No explaining, because that just invites argument.
If you can afford to buy a $1200 lawn mower that you don’t need, why not spend that money on a vacation or house repair, or something else that you want?