If sealing ammunition is such a waste of time, why is it done by every reputable military arsenal?
Why have all the police duty rounds that I've ever seen been sealed?
Why are there companies specializing in sealing ammunition?
http://ammo.hernon.com/index.php?option=com_content&view=article&id=13&Itemid=7
Just because you choose not to take the time to perform a particular step in order to increase the reliability of your ammunition doesn't mean that it's foolish or a waste of time.
As for expense, 18 to 22 grains of single base powder (I use old 4895 pulled from WWII AP rounds) in an ounce of pure acetone (not the oily stuff sold to remove nail polish) makes an excellent primer sealer and it's about as close to free as you can get.
If you like to use different colors to help ID your loads, just pull the guts out of an old, dried out magic marker and pour your acetone through that for color before you add the powder.
I'm not advocating that everyone should seal all, or even any of their ammo. I will say that immersion tests I've done on unsealed ammunition didn't give near the 100% sure fire results that others here have reported.
On the other hand, when primers are sealed with nitrocellulose and case mouths with Alox, I've had almost 100% percent fire rates with ammunition stored underwater at 5 psi gauge pressure (equal to @ 11 feet deep) for a week.
I only seal a small percentage of the ammunition I load, mainly large game and SD loads, but there's no doubt in my mind that doing so substantially increases the reliability of rounds that might be exposed to significant amounts of moisture.