It is also true in landtrading. The amount of ghosts you get is proportional to both the amount you grab, and the number of built acres on the target you grab, on top of that it is also affected by reset-long Country-to-Country DR. Not only that, Ghost acres DR doesn't get reduced by the target attacking, so even if his normal DR is say only 1 because he got attacked 10 times but attacked 9 times himself, his ghost DR is actually still 10 (based on old DR system before half-life).

You have the best results attacking a country of the same strategy as you, so you don't have to rebuild building types.

Also production is actually doubly important when landtrading precisely because of your losses. A good landtrader doesn't start trading until he has maxed out his agri techs. Weapons isn't important because breaks are intentionally kept low. Strat tech is important to max the land gains, so really the only 2 techs you focus on are those 2 (as a farmer trader).

Tech is self-fulfilling cycle. If you make enough money, it allows you to buy more tech to make more money to buy more tech... The key is to be in the upward cycle, not a downward cycle.

The loss of tech isn't significant because you also gain them when attacking (hopefully you are attacking the a strat country).