My daughter can't fathom her great-grandparents' lifestyle

My grandparents, so my daughter's great grandparents, are both 80. They live on a lake in MN, have a boat, a jetski, 4 bedrooms, a truck and a car both less than 10 years old. She asked me, "What did great grandma and great grandpa do for jobs when they were younger?" I responded "Great grandpa worked for the state, mostly maintaining stop lights. Great grandma was a secretary at a college." Her response was to go super quiet for half a minute and then she said "So you can get rich doing those jobs?" This kid is 6!! She already realizes something isn't adding up. If my husband had the same exact job that he has now, but set in the 1970s, we would be absolutely rolling in money. Instead we both have to work full-time to afford a 3 bedroom tract house (that we are super thankful for), and we've never had a real vacation. Trips, yes, we can afford ONE overnight in a hotel so we don't go very far. I also cannot imagine a world where any of our friends would be able to afford a third child. They all have zero, one, or two, and it all comes down to money. System is messed up.