In the absence of transactions costs…

When you take most three-year-olds shopping, they're happy if you buy them a
new doll.

Not Pipi Quinlan.  When she got on to her parents' computer, she ended up with
a $NZ20,000 (£8,000) mechanical digger.

The first thing Pipi's parents, who live in Auckland, knew of their child's
expensive acqusition was when her mother Sarah logged on to her computer and
found a series of e-mails from the New Zealand Trade Me auction site
congratulating her on her buy.

The toddler who usually prefers high-heeled pink shoes over giant yellow and
black diggers, had woken early and started playing on the computer while her
parents were asleep.

After a couple of clicks on the mouse, she entered the NZ internet auction
site Trade Me which her mother had logged on to earlier.

And so on.  Here is the story.