The after market tramps are excellent quality, albeit not class legal, if you want to race in Hobie regattas. Open regattas would make no difference.
The prices are radically different. The after market price is $275, see
http://store.catsailor.com/tek9.asp?pg=products&specific=jmpnrogpg0

The Hobie tramps start at $294 and are as high as $378. See http://store.catsailor.com/tek9.asp?pg=products&specific=jmmnnmjpq8

Then there is the bias cut tramp.., ONE-PIECE BIAS-CUT TRAMPS: H-14, One-piece tramps provide a smooth, uncomplicated deck. See http://store.catsailor.com/tek9.asp?pg=products&specific=jmoniqfrg4

For the best tramps available, we represent Sunrise, who is the leader in tramps. If you use Teflon stitching, they will just about last forever. See
http://store.catsailor.com/tek9.asp?pg=products&specific=jnkncrpng0

Hope this helps.
Rick