I almost exclusively carry a cheapo utility folder. Like Raffi said, I'd hate to lose an expensive knife. Plus, if I go somewhere where they are doing searches, and I forgot to leave it at home, I don't mind tossing it in the garbage. (Raf taught me that trick.)
A few years ago, Menards (a midwest building supply place, like Home Depot) had a closeout on small, black folders with a built-in, red LED light. They were selling them for $2 to $3 depending on the store. I went to as many Menards as I could & bought them all up (about 20 of them). It's been about 3 years & I'm only on my third one. (I tossed one at a function where they were using metal detectors & one broke after years of abuse.) They have even survived countless trips through the washing machine (I'm a knucklehead).
If I'm a bit more dressed up, I sometimes carry a Smith & Wesson SWAT tactical folder (about $35) because it's slimmer & can be worn more unobtrusively.
I totally agree with Raffi's point about using an expensive knife vs. a cheap one. If you are trained well, both are effective. For me, I can make do with a ballpoint pen or a credit card.