Yes and no. I had a shop fab up a dual for my MR2 once... labor was $270 (and that was 10 years ago) and still had to buy the two $150 mufflers... and they just basically welded onto my stock b-pipe. And as we know, MR2's don't have a very long exhaust route. Not to mention any generic garage will have mild steel mig welders or use flux core. Since their welding is pretty erratic at best it comes out looking like the tin man sneezed. Not the sort of quality I like when I'm paying over $300 in labor with $300~ in parts. At that point I think it's better to grab something from a respectable company, then all it takes is a few jack stands, some socket wrenches and a ton of PB blast (if you're like me and from an area with snow 5 months out of the year and they salt the roads).
Unless you have a friend that welds and likes weekend fab jobs for the price of a BBQ, 9 times out of 10 you get what you pay for... or you pay a lot and still get taken for a ride. Just been my experience. Which is why I fab up my own stuff now.