Hoes does Revenge of the Titans money flow work?

Recently I picked up Revenge of the Titans again. I noticed a lot has changed, upgrades no longer cost money, and half the game mechanics seem to have changed with it.

What I never quite could grasp in RotT was the money flow. I've been experimenting a bit with income, and it doesn't make sense at all. Building more refineries sometimes yield less income, taking the refineries tech path doesn't help a lot either. Sometimes I spawn tons of turrets, it feels like a bad attempt, and I end with tons of money. Next I build what feels like more efficiently, and I end up with less money :(

Some things I noticed so far are:

• There is a max of 4 refineries per crystal.
• Losing/damage to buildings is fatal for money.
• Replaying missions gives a huge randomness in remaining money.

I'm at loss for the money remaining at end of mission formula, as well as half the strategy guides I find are for old versions of the game. What would really help me too would be a lite of suggested amount of money win/loss per mission. I noticed that some missions let you gain 1k mineral easily, while others can only be solved with a negative total.

Solution 1:

The money that you carry forward to the next mission is simply to total of:

• any unspent money

• 10% of the value of all unmined crystals

• 40% of the value of all buildings that are still alive (the same value as if you sold them manually)
  Damaged buildings will return less than 40%, so this is a maximum

• any bonus awarded by medals

I believe the game also increases the difficulty if you have lots of cash, and reduces it if you're running very short. So don't worry too much about losing some cash over a specific level - the game should help correct for it.

With than it mind, I'd put forward the following advice:

• Losing buildings is very bad - not only to you lose their resell value, you often have to pay to replace them.

• Building too many buildings is bad - because you get less money back than if you'd just left it unspent.

• Selling buildings so you can spend more cash is bad - you're basically spending the resell value of the first building and devaluing it further by exchanging it for the (reduced) resell value of the replacements.

• Don't always saturate crystals with refineries - 4 × $250 refineries for a single $1000 crystal is a waste, in the end you only really get the resell value of the buildings back .
  I try to spend half roughly half the crystal value on refineries, so 2 for a $1000 crystal, 4 for a $2000 crystal and whatever makes sense for groups of near-by crystals (remember that a refinery can only work on one crystal at a time, but if the one it's working on is finished and another is in range it will start work on the second).
  Only use the booster buildings (Reprocessor / Collector) where you have big groups of refineries, they rarely make you more cash in the long run.

• Barricades and mines are a permanent cost - they can't be sold, so return no resell value at the end of a level. By this same token, don't be afraid to lose / use them, it's much cheaper than losing a real building!

• Don't focus too much on medals - yeah, you can get Efficient for mining all crystals before the wave ends, but it's only worth $500; if you have to spend more than that to get the medal (ie, three extra refineries) then it's not worth the effort!
  However, Careful and Pristine (awarded for no buildings lost / damaged respectively) offer a small bonus for simply playing well, so don't completely ignore these.

And finally, remember that you don't need to sell buildings manually, you automatically get the resell value of everything still alive at the end of a level.