In days long since past, a young man buying condoms had to get them from the pharmacist who kept them behind the counter. An eager but clueless young man asks the druggist for condoms and gets this reply:

Which package son? They come in packs of one, six or a dozen.
What do people usually buy?  
Well, the single pack is usually bought by the girl, just in case it gets hot and heavy and the guy doesn't have one. The six pack by teenage boys and single men, one for each day of the week except Sunday.  
And the twelve pack?  
That's for married men... One condom per month.  

The young man says:
I'll take a pack of six.  
Good choice! That'll be $4, and 20 cents if you add tax.  
Tacks?!? I Ouch, I thought you just rolled them on?!?