There are many vouchers seller, how they can get so many 100,75,50$ vouchers and make it a business; what is their secret?
Most of the people who buy Adwords don't use the vouchers. Also, you have to remember that Google Adwords is an electronic product, or in other words, something from nothing. Where thinks like iPods, sweatshirts, etc. have a production cost, Adwords' production cost is virtually nothing. All money made from Adwords is 99% profit, so Google can afford to give out more coupons than normal companies.