I have recently done all the math. I conclude that the best economy cards to pick are (in this order) (with the least cost/eco):
- 1-0 Engineer
- 0-0 Spike Factory
- 0-0 Dart Monkey
Full list: https://docs.google.com/spreadsheets/d/1WIAG3fmLMwAUfrZQNGLth1BjtOqcqU7zr1SLXByjTa0/edit?usp=sharing
The towers with the biggest discounts are in this order:
- 4-2 Dartling Gun (30,000 discount)
- 4-2 Super Monkey (10,000 discount)
- 2-4 Monkey Village (12,800 discount)
Here’s my video on the matter:
https://www.youtube.com/watch?v=mYKrOyWMCdU