The Replacements

I have friends who are involved in capitalist enterprises, may God bless their souls, and maybe one of them could shed light on the following conundrums:

 - - A man (let's call him "Mark") buys a cordless drill that comes with two batteries.  Some years later, both of the batteries are dead as mackerels.  He finds that the cost of replacement batteries is higher than the purchase price of a new drill with batteries.

 - - The same man ("Old Mark") buys a pc printer/scanner/toaster combination.  When the printer cartridges are empty, he goes to buy replacements, and finds he can buy a whole new printer for fewer dollars than the price of the ink cartridges.

 - -Guess who finds the same deal with a replacement wheel for the wheelbarrow which he wheels through streets broad and narrow.  A whole new wheelbarrow, although getting rid of the old one was a challenge. (I put it in the new wheelbarrow and pushed it around until I found someone who wanted it.)

On the same theory, I took an empty pizza box back to Pizza Heaven and asked if they would refill it, but while I was there, a police came in and asked who left the wheelbarrow double parked out front, so I had to leave.