GrandFather

Grandpa & Grandma were visiting the kids overnight when Grandpa found a bottle of Viagra in his son's medicine cabinet. He asked the son about using one of the pills, and the son said, "I don't think you should take one; they're very strong and very expensive."   

"How much?" asked Grandpa.   

$10.00 a pill answered the son.   

"I don't care" said Grandpa, "I'd like to try it and I'll leave the money under your pillow as soon as I break this $50.00 bill."   

The next morning the son found $110.00 under his pillow.   He said to Grandpa, "I told you each pill was $10.00, not $110.00."

"I know," said Grandpa, "The extra hundred is from Grandma."