Buy in.
Right now, there are three ways I know of for a person to start getting into D&D 4e: 1) The starter game, 2) D&D 4e for Dummies, and 3) Keep on the Shadowfell.
The starter game has pre-generated characters. It was designed for people to graduate to the PHB1. It has tokens, tiles, and miniatures.
D&D 4e for Dummies is geared for players and contains all the side bars and extraneous info one gets in the Dummies line. It also doesn't have an adventure or any other equipment. The DMing 4e for Dummies doesn't have an adventure either, but does go over the one in the DMG1. The Dummies books seem to be geared for people like Shelly Mazzanoble who get invited to join a group of experienced, adult, players.
Keep on the Shadowfell is free, has pre-generated PCs, and a map. It also has quickstart rules.
If someone wants to go on from there, the buy in is whatever you paid for the starter set + the PHB1 + an additional book if thats where your class is.
What's missing is something that has character creation + equipment + errata. I think the new box set fits nicely. Also, the buy in becomes $40. (The price of the red box + the price of the player essentials guide.) That's 30 levels of entertainment. The PHB1 is $5 cheeper, but doesn't have errata or equipment.
The buy in for a new DM is, as is so common to me by now, more expensive. With the essentials, it's $60. That's $20 for the red box + $40 for the DM kit. That gives you a total of 3 adventures and a 256 page book on rules and advice. (The 4e DMG is 224 pages!) You also get dice and tokens. Not bad. The only problem that I see is that this doesn't seem to amount to 30 levels of play like the player buy in does. However, if they're smart, the two adventures in the DM kit will fill out the heroic tier. At that point, the new DM will have enough experience to either make his own adventures, or buy some.
Bill says he the essentials line will be the starting point for new D&D players. This seems to be the cumulation of "everything is core" motto of 4e marketing. Theoretically, these people could buy the Rules Compendium and play for years, through 30 levels and never touch the PHB1, DMG1, or MM1. And I suspect this won't be a theory in couple of years.