I've been interested in photographing bees recently. Rather than buy a macro lens, I spent $32 on a 10mm and 16mm Meike extension tube. Photos are with an A9II + Sigma 35mm f/2, which normally offers a 0.18x magnification. All four are taken as close as the lens will focus. I'm very happy with image quality, especially given that this lens doesn't have a super flat focal plane at its minimum focal distance.
For anyone who tries an extension tube for their first time: you won't be able to focus very far in the distance (beyond about 1 foot in my case). Be ready to get up close and personal.
I do like the idea of flipping a lens around and am very tempted to give it a shot. I feel like this would work better on manual glass. Most of my mirrorless stuff is focus by wire, with the exception of an older sigma 35mm. They all have electronic apertures :(
I was shooting on Nikon back when I was experimenting with macro, and the reversed lens I was using was a nifty fifty.
I think part of the reason I ended up getting more into landscape panoramas than macro was that the cost of entry for high-quality results was lower