Those claw machines are scam one...
Basically, the claw will only be pressured sufficiently to grab
anything after X amount of tries. If its not the "X" try, it
will be a strong as a limp dick's ability to lift a
laptop.
The trick to winning at those machines is to watch people play,
and wait for a bugger to win or notice a significant increase in
strength of the claw. Then start counting the number of
attempts until that increase comes back again. That is the
"X" factor.
Then, simply wait for the next "X" and be the one to use the
claw when it comes around.