What you guys forget was that NASCAR was dragged into all this back in 1980's when the manufacturers switched to front wheel drive on the majority of their cars. NOBODY was going to watch 4 cylinder or 6 cylinder production cars with plastic front and rear fascias race anywhere. They couldn't keep racing 1970's type cars because they were out of production and no manufacturer was going to back a series like that. The only rear wheel drive production cars back then were the 4 door luxury cars and that wasn't going to happen. They did what they had to do to keep the series afloat and by the 1990's Nascar racing reached it's peak.
As far as engine technology goes I worked at Dodge Motorsports from 1966 to 2007. All the manufacturers had special built race engine parts made for their cars and a lot of those parts were not available to the public. When we at Dodge got back in 2001 we had to design and build an engine that was built to Nascar specs since none of our current V8's back then would work. Same thing when Toyota got back in.
And as far as keeping costs down technology costs money. Back in the 1960's and early 1970's teams didn't have their own engine dynos or wind tunnels etc. They depended on the manufacturers to help them out. That has all changed now. And besides everybody is going to do what ever it takes to win no matter what series you run. Back in 1978 our goal at Dodge was 600 HP at 7200 RPM for the Daytona 500 and we made that goal. By 2012 when Nascar switched to fuel injection we were making over 900 HP at 9500 RPM still using the same displacement (355") and the same carburetor (Holley 4150). That extra 300 HP came from exotic materials in the valve train so the engine would spin higher, hours and hours of time on the air flow benches developing new intake and exhaust port configurations, and the same thing for camshaft development and dry sump oil systems. And gentlemen, all that development costs money. And he who has the most money wins. Look no further than Mercedes in Formula One.
You want to talk about change in racing. Look no further than Top Fuel Dragsters. They don't run the quarter mile anymore.............they only run 1000 feet instead of 1320 feet. The engines make anywhere from 10,000 to 15,000 HP depending whose numbers you believe. They run around 3 seconds and 340 mph in that 1000 feet. If they ran the whole quarter mile just think what their top speed would be! The sanctioning bodies are try to keep the cars and drivers safe and still make the racing competitive.