That's a very famous picture. $7,000.00 was what a Cadillac or even a more ordinary Ferrari would have cost you back then. Rolls Royces were about as expensive as cars got, and were thought to be priced to match the cost of a modest private home, i.e. around $10,000.00. And that particular rail is an interesting one, since it's a combination of a "production" chassis, a Dragmaster Dart which you could order from a catalog, and a very special, virtually one-off motor, a Pontiac built by Mickey Thompson with his then-experimental hemi heads. I doubt that more than a half dozen of them, if that many, were ever produced.
But the point of the picture is that you could go Top Fuel racing by ordering up and building a competitive machine from readily available parts. This was a relatively new phenomenon, something which emerged perhaps 5 years earlier. Today you can do the same thing, but rather than costing you the price of Cadillac ($50-90K max) it will cost you at least the price of a Rolls Royce ($200-300K). And the actual racing is more heavily regulated, less generally available, and far more expensive.