I’ve wondered about the supposed differences between the cheap and expensive ear plugs, too. I’ve read that the expensive ones have a flat attenuation over a large frequency range, whereas the cheap ones may attenuate part of the range more than other parts.
I’ve never been able to tell the difference between high fidelity sound equipment and my cheapo Sony boombox, so I suspect that the expensive earplugs would be wasted on me, too.
I keep sets of AO Safety’s yellow foam plugs all around (car, shop, bedroom, suitcase, gig bag, etc.). They cut the sound levels well, are easy to use, and are very cheap. I’ve also used some of the silicon rubber ear plugs with flutes (a series of floppy ridges that engage the ear canal). I find these often irritate my ear canal, so I can’t wear them for long.
That’s why I prefer to wear the headset style if possible, especially when working with noisy power tools or mowing.
I have tried some Hearos “Ultimate Softness Series” foam and Hearos Rock 'n Roll ear plugs. The foam ones are rated at 32dB noise reduction, but they keep sliding out of my ear, so in truth the noise levels aren’t reduced at all. The Rock 'n Roll plugs (NR: 22dB) work pretty well. But they don’t reduce the noise as much as the headset style or AO Safety brand’s cheap yellow disposable foam ear plugs.