The rest of us are just barely scraping by whilst financing them.
Typically the young receive more than they produce as the largest benefit is a free education. After that, the individual goes thru their productive stage and receive far less, very little, or nothing. But eventually the old age entitlements kick in and depending on how long they live, can receive benefits far exceeding what they have paid in during their productive years. Pity the man who paid into his old age entitlements then died at age 64.
I guess the collapse comes when the takers are outnumbered by the makers.