The buy your own points thing is always a scam unless you just need extra points to top off a purchase (you're 1,000 or 2,000 points short). Just calculate the amount of points it costs by 2.7 Cents, then compare that to the purchase price with the deal. Even with the 40% bonus, it costs a bit less than face value.
If you think about it, if you earn 3 points per dollar with the AGR Card and 4 points (double days) on Amtrak travel. You can earn 7 points per dollar on Amtrak travel during double days! So if you spend $100 on Amtrak that's 700 Points which is worth $20 in travel. There are plenty of other ways to boost your points balance than purchasing them!