I have never bought anything direct from the Mint and I don't plan too. I have heard too many horror stories about their service.
The mint operates under government control. What if either thing is true, that there is less gold than the government claims, or that they plan a gold grab to help fix the economy. last year they sold over 190,000 ounces. At today's prices that is a lot of money even by greedy government standards and, it heads off any resistance to our increasingly worthless currency.