The $12 router bit I almost returned is now my go-to for drawer boxes

I was cutting dovetails for a set of walnut drawers last month in my shop near Albany and kept getting this rough edge on the inside corners. Tried slowing down the feed, sharpening my chisels, even adjusted the fence twice, nothing fixed it. Finally my apprentice grabbed this spiral upcut bit I'd bought on a whim for $12 at a hardware closeout and swapped it in. The difference was night and day, clean cuts with zero tearout on the end grain. I think the geometry just clears chips way better than the straight bits I'd been using for years. Anyone else have a cheap bit that outperforms gear costing three times as much?