Technically the event is only 3 hours, they are just letting those ticketholders check in early (like the party). From the Parks blog:
“Disney After Hours” is a three-hour event that will take place once the park closes on the following dates:
- April 14, 21 and 28
- May 5, 8, 12 and 19
A separate event ticket is required for “Disney After Hours.” Guests can check in starting at 7 p.m. each night, with the event hours from 11 p.m. – 2 a.m. Pricing is $149 plus tax for both adults and children (ages 3-9).