First off, I am NOT telling you to do this or that this is a good deal. There are SO many better ways to get Skymiles like getting a DELTA AMEX card or sending points over from SPG points or maybe from your AMEX Membership Rewards points. All of these give you good value if you need Skymiles.
However, if you need just a few points FAST to book an award ticket then paying ½ cent each to transfer from, say, your wife or brother is cheaper than buying points outright. Also, these point transfers tend to go fast from one account to another (instant or inside 24hrs most times). The other reason may be that one of you is PM or DM and the other is not and you need just a few points to book a trip. Booking from a PM or DM account gives you the chance to cancel and redeposit free if before 72 hr window.
So don’t go do this one unless you need it! – Rene