There is several models between $10-$30, all cheap, all come from China, if you see others with a near identical look, it's a white label Chinese model. Pretty much anything in that price range is.
They all work decent enough for design work and even general 3d printing. You start see their limitations in 3d printing only on high end printers and rough milling work and even then you have something to compare them to, otherwise they work fine even then. They are NOT at all good enough for precision machining when you need precise, tight fit, but you don't need that.
Good, name brand, quality ones, are not going to sell for $30, or even $100, they tend to be near $200 or more.
If you want a really good one but not willing to spend $200+, check Ebay for used. I grabbed a last gen Mitutoyo for $80. Just beware, there is a TON of fakes of the latest gen, if it's a Mitutoyo for $30 or $40 or even $80 new, it's fake as hell and you would be just as good spending $20 or 30 on something else because inside it's the same thing. Mine doesn't have a thumbwheel (bummer) or do fractional inches (meh), only decimal and metric, while my Chinese white label does mm, decimal inch and fractional inch and has a thumbwheel (it also eats batteries at 10x the speed). All that said, my 3d printing quality and precision did go up when I got the Mitutoyo, something I didn't expect, but I wasn't having problems with the Chinese one.
