I'm really kinda asking if the megaminx at cube4you.com is REALLY 5 dollars...
It is. But the Chinese reproduction is of far lower quality than the original puzzles, and currently no one sells the originals comercially. When you find them on ebay, expect $75 or greater.
The first Megaminx style puzzle to hit the market was the Hungarian SuperNova, and is of very good quality. This is the same size as the later released Tomy Megaminx and Meffert's Megaminx, but the cuts are deeper so the edge pieces meet in a point (the Chinese version has these same cuts): http://twistypuzzles.com/cgi-bin/puzzle.cgi?pid=651
The Tomy Megaminx http://twistypuzzles.com/cgi-bin/puzzle.cgi?pid=649
and Meffert's Megaminx http://twistypuzzles.com/cgi-bin/puzzle.cgi?pid=654
seem identical, but Aleh (who built the Brilic) based his on a Meffert's core and says they are different internally. I only have a Tomy, so I can't say what these differences are. The other difference is cosmetic, the Meffert's (12 color) is tiled, not stickered.
The Chinese reproduction has had two versions. I think the older is still sold for about $1 cheaper, but I hear the newer is quite a bit better. I only have the second but I believe both are the same size, which is larger than the other puzzles (about 70mm face to face instead of 65mm). They have pips on their corner inside faces and dimples on their edge inside faces so their movment clicks into place for alignment. If you search you'll find that some find their movement much better if you file these down.
They have tiles instead of stickers, and their quality is not great. Watch out for sharp edges on the pieces, and for the puzzle popping pieces.
Any Megaminx will probably need some amount of work to be really great to play with, but the originals still seem the best. I find my $5 Chinese version to be OK and a good deal for the money, and I hear they can be made much better. But I prefer my Tomy or Supernova.