My son's team hosted a scrimmage Saturday. The lady who is employed by our school district was there collecting $3 from adults and $1 from students (same as reg. season). I'm not sure what the gate fee goes to support, but I do know the ~$15k of improvements to the field came from parents / fundraisers.
The lady is vey nice, and was appologetic for having to charge folks to watch a scrimmage. If I recall correctly, the fee goes up to $5 & $3 for state playoff games.