.99 vs 7.00 = cheap & dirty vs. doing it right
If it's peace of mind you're after, use the product meant for the purpose. That's what it's made for.
For practical purposes, and using the ammo inside of say 5 years, I wouldn't bother. Commercial shotgun ammo which IS sealed on the shot end, and which could very well be dropped in the water by a waterfowler, or the mud or dewy grass by an upland hunter, then picked up and used--successfully I might add--is NOT sealed on the primer end. The press fit of the primers suffices. Does that tell you something?
Now if you're making ammo to stash away not to be used until TEOTWAWKI, that's another matter. But in that case you won't care about spending the extra 6 bucks.
God Bless America