My parents in law are very money savvy. Neither of them have ever had jobs paying over 20k, I honestly dont know how but they managed it even writing it down it doesnt seem to add up to me.
They bought some run down flats when there was a property price crash, rented them out for years, sold them, had some very small investment/involvement in friends/families small businesses that paid off. They will go shop to shop doing price comparisons to make sure they get cheapest deal, they'll massively bulk buy items in sale. They change providers constantly. Did lots of little extra earners e.g car boot sales, selling things on Ebay, he would hire himself out as a man with a van on evenings/ weekends occasionally. She would occasionally help a friends business with deliveries.
They paid off their mortgage at 40, now in their late 50s, have a holiday home, range rover, 2 boats, and a few hundred thousand in the bank and both will have very generous civil service pensions.
Me and my partner make quite a bit more than did, but are no where near savvy enough (or can be bothered to live our lives that way) to maximize our earnings that much. (We would also never be able to buy multiple flats these days).
I dont think it's a class thing personally, just some are better at it than others. If you are completely skint however you dont have the luxary of being savvy and forward thinking, you tend to have to do whst it takes to tackle things in the now, like bulk buying wouldnt be an option, or small investments.
Maybe it's not a class thing but a job thing, perhaps if someones career involves strategy and maximising profit, making plans etc they adopt that in their own lives too.