One of the strategies to earning some funds on DCity is to receive technology cards from the game and then sell them on the market. Many of the tech cards aren't stackable either so there's no point having multiple copies.
So I am selling 2 Basic Automation cards. I don't have factories so the added bonus from them doesn't help me. If someone wants to improve their factories then please consider buying.
The Voice To Skull is an interesting one. Expensive card and if I understand the numbers correctly, there aren't too many of them out there. I'd really like a Neural Network so if i do manage to sell it, I will divert some funds there. The rest of it will go to the ice-cream parlor empire.
Overall, I haven't had that much luck selling technology cards but I did have a dry spell where I didn't get much of them. Now that I am starting to get some at a more regular pace, then maybe there's some promise to the strategy.