Joe Montana -- Hails a Yellow Cab ... It's Just Not Fair.

Here's NFL legend Joe Montana leaving LAX Wednesday in a taxi (not a chauffeur-driven black car) ... which is fine ... but it reminds us how LITTLE he got paid compared to the guys who came after him.

We pulled some numbers ... back in 1990, Montana signed a contract that made him the highest paid player in the NFL -- a 4-year deal worth $13 million ... that's $3.25 mil per year.

It's peanuts compared to today's top QBs -- with Aaron Rodgers inking a 5-year deal worth $110 mil, Russell Wilson has a 4-year $87 million contract ... even Eli Manning's making $84 mil over 4 years.

Even with inflation, Montana's annual $3.25 mil salary from his '90 deal only amounts to about $6 mil per season today.