I know in PA, the fines for a bicycle infraction are much less than for automobile infractions. Sounds like the cop may have stuck you with fines for an automobile. I would check the law.

Chapter 35 - SPECIAL VEHICLES AND PEDESTRIANS
Subchapter A - Operation of Pedalcycles (Bicycles)

"Section 3502. Penalty for violation of subchapter.
Any person violating any provision of this subchapter is guilty of a summary offense and shall, upon conviction, be sentenced to pay a fine of $10."