I occasionally visit the same Peoria Gander Mountain store referred to by the OP, and what he says rings true. They previously boasted large fishing, camping, and clothing departments, most of which is now gone. I suspect this realinement is due to the recent opening of a very nice and well-managed Bass Pro Shop across the river in East Peoria conquesting their business on those items.
When this GM first opened, they had competitive prices, good sales, and a full-service gunsmith on-site. I spent a LOT of money there.
Several years ago, they closed the gunsmith down, and prices started to rise. They also lost several knowledgeable gun counter employees (one of them the manager), and their buying policy on used guns got ridiculous to the point of insulting.
I always thought it was a big mistake to shut down the gunsmith. As far as the prices, a couple pawnshops in the local area have far lower prices on ammo and reloading components. If the "new" Gander Mountain wants to compete, they better take a look at their competition and adjust their pricing accordingly.
Just my .02.