The only mileage run I ever did was in the summer 1988 I believe. Pan Am had a deal that was something silly like (IIRC):

Each Shuttle flight earned 2,500 miles
Each Same day RT earned a 5,000 bonus
Fly more than 8 segments on the shuttle in a month and get a 10,000 mile bonus.

They also sold a student book of 10 shuttle flights for something like $299.
I had a special coupon that got me 25% off of any Pan Am ticket that was about to expire.

I was also Platinum on Pan Am so got a bonus on that as well

So for $275 I flew back and forth all day and got something silly like 80,000 miles for it, which in those days was something like three Economy tickets to Europe.