Discussion of level 4 monsters.

That's an interesting example. Why don't you try it the other way around – when you have 1 city against 10 cities and 100 mines belonging to the enemy? :D
If you're building a city from scratch, Crusaders and Cavaliers will require the least amount of money, and roughly the same amount of ore and wood – a total of 134 units.
If you're building Angels and Monks (the construction time is the same), it will be 1000 gold more expensive, with 72 less wood and ore, but an additional 25 crystals and 14 gems.
If you're building Angels and Crusaders (1 day longer), it will be 4000 gold more expensive, with 42 less wood and ore, and an additional 17 crystals and 14 gems.
Oh, what strong funding for the Angels... Cavaliers only require 33,500 gold to build, not counting other expenses – very little... :eek:
Is it difficult to find an extra 1000-4000 gold or crystals and gems? You can sell excess sulfur and mercury, as well as wood and ore, at the market. :D
Of course, this doesn't mean that you can't fight with Cavaliers – you can and should fight with them, it's just that Angels are often preferable.