The Sog Flashes have a world-class clip and that's the best thing I can say for them. I gave mine away.
The Persistence is one of Spyderco's best value knives and the blade is one of my favorite shapes. If you don't mind the somewhat bulky frame, you can hardly do better for the $$.
The Skyline is a personal favorite in my current quest for lightweight folders. The designer gets top marks, IMO, for managing to put so much into such a small frame.
The thumbstuds don't work as thumbstuds, according to the manufacturer's marketing veep, only as a blade stop. Which is unfortunate for those of us who favor studs. But the flipper works extremely well on my three Skylines (a black handle, a red handle and the last one I could find with a Damascus blade.) You might want to oil the blade, which is bead-blasted and can rust, instead of stonewashed as Kershaw has advertised. If those things aren't an issue, the Skyline is top-drawer for pocket carrying.
One of the small Buck Vantages (the S30V Pro) also is one of my regular pocket carries. The small Vantage also comes in two high-value less expensive versions. The blade length is a convenient 2 5/8 inches.
The clip is deep-pocket and every bit as good as the SOG (but not black, unfortunately.) The drop-point blade is not quite as good for slicing as the Spyderco and Kershaw, but it is strong, has a flipper and a hole-opener, and easy to carry and fun to use. Another great folder for pocket carrying.
The Skyline and the Vantage may be a few dollars over your $30 mark.
Hope this helps.