Replacement seat belts-Best deal

I am rebuilding a 2006 Pontiac G6. The car has a blown driver's side air bag and both front seat belts need to be replaced because they activated also. I noticed Ebay has replacement seat belts-after market for less than $100 for a pair. OEM replacement seat belts are $280 to $400 for a pair. Has anyone used the aftermarket ones? Do they interface and function with the car's restraint system like the OEM seatbelts? Do the pre-tensioners work the same? Would like feeedback from anyone who has used the aftermarket belts?
Thanks.
Bob