I struggled with this too as I couldn't fathom spending a mortgage payment on mufflers.

I bit the bullet and went with Borla S-types, best decsion I've made.

Aside from that, your buddy's best bet is to locate a set of used GT500 mufflers and have a shop weld on the correct inlet size to install them.

 

GT500s are gonna be your only option on the cheap unless you can find someone selling another brand used on the cheap.