For handguns, I can spend $5 and the local gun shop will put them in their ultrasonic cleaner... takes a few minutes. If I do it myself, it doesn't cost much less (considerng the price of cleaning supplies), and it takes about 20 minutes per handgun.
Semi-auto rifles can take 30-40min, especially after shooting corrosive ammo.
Bolt & Lever action guns are pretty quick, anything more than 10 minutes (even after shooting corrosive ammo) is just wasting time.
My pump shotgun (Mossy M590-A1) is a beater, it goes in the dish-washer with a light coat of Simple-Green and then sprayed down afterwards with WD-40 (swabbing out the mag-tube, of course, to prevent it from deactivating the ammo)... and that's only if it needs to be cleaned (muddy, etc). Most of the time just a pass with a Bore-Snake will do.
I love Bore-Snakes, btw.