Aside from that one tiny cheap toy in the sears catalog backnin the day, my recollection was starting price was around $250 for any tumbler(dad was considering them for years is the only reason I have any recollection). The $52 Harbor freight option is an impressive deal especially considering a few decades of inflation. I'm not say they were ever affordable toys, just that they are more affordable than they used to be. Size is a pretty big limitation on most readily available ones below the $500 mark.
It's a cost vs reward thing... so take this with a grain of skepticism, but, if durability was the sole consideration, nylon filament might give the most. nylon is very slippery so it's unlikely to abrade as fast. (this is why it's used in plastic gears.)
I think nylon does well with sliding friction, but have some concerns about whether it would hold up well to the kind of sharp edges you tend to have with abrasive media. That's from some observation on both commercial rock tumblers, industrial ball mills, and abrasive blasting equipment. I won't say I know enough from experience to say it will work for sure though.
won’t say I know enough from experience to say it will work for sure though.
there's "working" and then there's optimal. lol. pretty sure you could drop some media in a martini mixer and hand it over to sugar-crazed kiddies and have it "work". I accept no responsibility for that inevitable disaster,
that said, I suspect that depends on the kind of media used. sandy grit in a water solution or something would probably be fine.