I've been in the past, but have never lived in New York until this year, meaning I could go mid-week rather than planning a weekend trip around the tournament.
I bought a night session ticket a month in advance for about $40 - only later did I find out that the US Open was featuring free grounds admission day on the second Thursday of the tournament, a first in Open history.
Grounds admission doesn't grant access into Arthur Ashe Stadium (where the headliners play), the day would mostly feature doubles matches and juniors, and the tennis center would likely be claustrophobically packed with fans. Regardless, I had to capitalize on this freebie.
Having already been to the night session during week one of play and scouted out the grounds, I felt prepared to do this day on the cheap.
I spent $5.50 on transportation and splurged on a $15 souvenir, and it was the farthest $20.50 has ever gone for me.
Here's what I got to see: