Minus the slavery, have we really expended that much human effort and equivalent wealth and time on something in the modern era? The only thing I can think of is Free software products, shit like Linux.
[citation needed]
The 10th-tallest pyramid was built in Memphis, TN 30 years ago [0] and it's now used as a Bass Pro shop. Say what you will about working conditions in the US in the 90s, but I don't think it'd be fair to call it "a super-feudal economy and society".
That said, pyramids seem to have been built with hired labor so the point is pretty muddy regardless.
You know what's today's 4000yr long monument to vanity? Elon Musk's orbiting Tesla