A few of us have intellectualized this situation the same way you are - and the 50元 or 200元 fine does seem quite small, especially compared against the investment of a 沪-A Plate.

But you may also want to look beyond the fines and consider the potential liabilities if you find yourself in a bad situation while riding downtown with just a 沪-C Plate. In this case you are illegal and you could be arguing that the farmer and his truck of watermelons pulled out in front of you without looking, but he will have a different story and he may have all of his paperwork in order, unlike you.

As you can see there is security with the 沪-A Plate beyond just immunity from the stops by the police - and these stops for both ebikes and motorbikes are greater this summer with the Expo happening.

No one wants to pay the huge amount for a 沪-A Plate, but if you can find the resources then maybe you should consider it a "deposit", rather than an expense. As the plate system works now, you can always put your plate back into the auction system for market price which is currently trending up and up.

* Caveat is "as the plate system works now". TIC