I've never owned a designer bag - not because I'm against it, but because practicality & quality come first for me, then unobstrusive logos & a round shape. I only consider a bag if it ticks ALL my boxes, no matter the price, but I think the most I've ever spent on one is £100-£150.
In the past, I've spent anywhere from:
~ £7 on the Uniqlo half moon bag (guess it wasn't selling as well over here so I bought it discounted for hiking - before it went viral!)
~ £10 on my teal oval belt bag (a surprising workhorse, since there's no way it's real leather but it hasn't flaked or peeled with almost daily use over 3 years - bought on a whim because of its handsfree convertibility)
~ £80 on my Steve Madden Bbrenda sequin purse (I expect to keep this one for life - convertible from a circle clutch to crossbody with a double zipper for security!)
~ £100 on my chocolate leather backpack (bought from the men's section because I needed something with a padded laptop sleeve but also wanted a curved top).
~ I also have a circle backpack for city excursions, a straw circle crossbody for the beach & a travel backpack, but I don't like having to switch things out regularly lol.
TL;DR: I'd be open to a designer bag if it was curved, sturdy yet lightweight, practical to carry, big enough & in my autumnal colours. That's not a huge ask, is it?