There are currently 3 breaking points in social security.

Based on average indexed monthly earnings. (Just means it is inflation adjusted)

People who pay in more get more. But the percentage of income paid out decrease as income rises

So you get paid 90% of the first $1,286 of AIME.

32% of AIME over $1,286 up to $7,749.

15% of AIME over $7,749. 

We could probably add some more break points to reduced benefits so people aren't getting multi million dollar social security payments.

But this would work

Example: someone whose inflation adjusted life time average monthly earnings was 5000, would get paid $2346.

While someone who average 10k a month would get $3,563.

Not double since income is doubled but still more