incentive

my sister received P250 credits to spend on any deal from a group-buying site.

me:  'how come they sent you that?'

sister:  'because i buy from them...'

me:  'i buy from them, too...  how come they didn't send me?'

sister:  'maybe it's random...'

we check her account.  she hasn't bought anything from the site!

me:  'you haven't bought a single deal...  i've bought a lot!  why didn't they send me???'

sister:  'oh...  maybe they sent me so i'll buy from them...  you've bought a lot so they don't need to entice you...'

oh...  ok...  : }