I feel your pain. Even if the dealer did replace the exhaust manifold, you still would most likely have the same issue down the road.
It seems that the manifolds warp like hell and break the bolts, and once they are sanded or milled flat, they never do it again.
A very common issue, so many here have been through it. All that can be done is pay to have it fixed, or DIY.
I let mine go for way too long, prob 40k miles or more, until I couldn't take it sounding like ****, then I caved and fixed it.
2015 Ram 1500 SLT QC 5.7L 2WD 110,824 miles on the odo. Well, I have been noticing a cold-start tick on passenger side that subsides after warm-up. Been hearing it for awhile (hoping that I wasn't hearing it), tugged on the heat shield, and it appears the top rear stud has parted. Too early...
www.ramforum.com
I'm sure you might find a decent exhaust shop in your area where you might find a decent price, all you can do is ask around. See if they machine the manifolds, etc.
Wish you the best for a complete and lasting fix.