A750SCORE wrote:I wanted to know how come the price of Kaplan Math Work Book is $20 on Kaplan.com but $13.00 on Amazon?

You'll find that many wholesalers sell items cheaper than the creator of an item.

In most cases, it's because the originator of the item wishes to maintain a good relationship with its retailers and doesn't want to undercut them. For example, if you buy computer software, the manufacturer almost always sells it at the highest price while retailers are often a cheaper source.

Just the way the retail world works, nothing funny going on.