I was just riding with Westerville PD and we had talked about the same thing.
Its common that drunk drivers fail to turn on headlights while driving, therfor he saw opportunity to pull you over. At 10pm with no headlights you could have caused a SERIOUS accident, so he had probable cause to pull you over.. its 10PM.. Why werent your lights on? 10pm = very dark outside.
Most of the time, yes, you do only get a warning. However, in this case, maybe the officer was having a bad night, or maybe you have other traffic violations too? Maybe you were cocky with him, or just plainly displayed a bad attitude. Hell, maybe you just had some bad luck for the night.
Busted. End of story. You could try and plead no contest and have the fine thrown out, but either way youre still stuck paying court costs now.