One of things I hear people talking about concerning buying musclecars around the 1970 time period was how bad insurance rates were for big engines, and even getting a 4 speed could make getting insurance unaffordable. Sometimes we'll see a car with a 3 speed stick and wonder why the original owner didn't spend a few more bucks to get the optional 4 speed, but even the differerence in insurance between a 3 speed and a 4 speed could be big.
I don't have the figures for how much the cost of living has gone up since the '70's, but I would guesstimate maybe 3X since the late 70's and 4X since the early '70's? I got my first "real" job in late '78 at a grocery store bagging groceries part time for $3.65 an hour, I was happy to be getting a paycheck, but even though I was living for rent free at my parents, I wasn't swimming in money on the $70-$80 a week I was making. I was able to save enough cash to buy a new Gibson Les Paul on sale for $575 a year after I started my job, what is a LP custom now, $3000? And after getting promoted to stock boy making $6 an hour, when I was 18 I paid $6100 cash for a 2 year old Bronco, how much is a 2 year old SUV now, maybe $25K? I remember premium was around $.75/gal when I first started driving, but gas had "spiked" up to $1.25 for regular when I bought the Bronco in '81, which is the main reason I got it for about 1/2 what it had costed new.