Last year (2016) was my first true mileage run. SEA-JFK-SEA. I boarded at around gate D12 in SEA, landed in JFK, re-boarded the plane, which then taxied into D13. That was 5000 miles to go 50 ft.
Airfare was around $250, but I was targeted for a SEA-JFK/vv double RDM on AS, so that was about 10,000 RDM for $250. It was not the best, but I needed to top off my account for a J ticket from SEA to S. America.