I played in a US Open qualifier in Philly a couple weekends ago. It was very well run, and a good experience for me. 28 players came out. Originally, it was going to be 2 qualifiers per 32 players, based on MR's quota. A couple weeks before the event, MR changed their policy and the promoter can send as many players as he/she wants. So this promotor had enough money from the entry fees to send 4 players, plus also pay a bit of cash to the top few players. $170 entry, with $20 of that going to admin/Green fees.
The field was mostly 500's from what I recall. If you are a 600 player, you are probably 50/50 to get a spot, in any qualifier in the country, IMO.
Here is the bracket:
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I played Jeremey Seaman on the stream table for the first round, and had a good time. The other player that beat me was Trenton Marty. He's in his late 70's, and is probably going to be the oldest player in the Open. Both of them got a qualifier spot, along with 2 others.
A week after the event, the promoter made a FB post that he has a few "promoter spots" to anyone that played in his qualifier. If we contact him and ask, he can give us the spot to enter the US Open. It will be completely paid out of our own pockets.