[quote name='kevgret']So instead of paying the equivalent of $56,000 in purchases you only need to pay $28,000![/QUOTE]
To be honest, those reward programs don't really work out for people that are seeking particular gifts and have to up their spending to meet them. However, if you are a business traveller/etc. and have to spend the money anyways, throwing it on the AMEX for a free 3DS is a nice deal. Given an average 3% rate on purchases, they are giving you about a third of their profits ($750) back, ignoring fees/discounts they get/higher rates on smaller businesses.
Rewards programs are good, as long as you don't adjust your spending levels to get rewards. Who can argue with getting something when you would otherwise get nothing?