Wow this thread ...
Megan Exhaust - 500 ... cheap you get what you pay for
Fabspeed - ~1k ... straight pipe setup pricey but you know exactly what you are getting
Arkapovic - 6.5k ... Seriously overpriced but a full titanium system - hey if you got the cash then more power to you ... they also have downpipes at 2.8k
Eisenmann - 4k ... Seriously overpriced for just an exhaust OEM doesn't even cost that much to replace.
I run the fabspeed exhaust and love the sound personally.
The thing to remember when buying pre-built exhaust systems is you are not just paying for the metal, your paying for the brand, r&d, build and shop time etc and you know exactly what you are getting and paying that damn M tax.
If you want a simple straight pipe setup it can be done for cheap as others mentioned, you can pick up resonators the piping and get a shop to weld it together but until you built it there is no idea how it will actually sound ... this would probably cost around $300-500+ for the metal, fabrication and install unless you have a shp that can hook you up for cheap.
I chose the fabspeed because I didn't want to hassle with building my own and not end up being satisfied with it ... and I sure as hell am not dropping 4-7k on something that is 100% for your ears only, the gains from an exhaust on this truck are so small you will never notice it.
The Arkapovic posts a 11+HP gain that puts it at about $590 for each 1HP increase