You get money simply for having the trade port's cargo ships in existence. Trade ports have a high spawn rate, and ships have a good deal of health, so it's extremely difficult to put more than a pitiful dent in someone's economy by killing his cargo ships.

The problem is two-fold; each trade port produces A LOT of trade ships, and players build A LOT of trade ports.  I do agree that something needs to be done here because there are simply too many of these guys running around late game.  Certainly from a balance perspective trade ports are just unreasonably effective, especially when compared to refineries.

Individually, yes. However, players tend to build a LOT of trade ports, as they're the #1 "filler" structure to get. As a cargo fleet, the numbers add up very quickly. Add in the respawn power of all the trade ports(game files say 12sec), and it will take you a MASSIVE arsenal to consistently KEEP the ships dead. 500 hull points(+ upgrades), every 12 seconds, for every trade port is no joke, and you'll have a full time job trying to place a complete trade embargo on anyone.

On the plus side, cargo ships give 5XP each. The potential for undending carnage gives you a risk free method of power levelling your capital ships, as long as you can find an unoccupied trade path.

Side question: Do the factory boosting techs (industrial juggernaut + relativistic factories) help out trade ports?

Just sit some carriers outfitted with fighters in an empty grav well and they will do the job...

Incidently - what are you running this on to get that much lag??? You could try turning down some graphic options or something. My machine doesn't slow down (that I can notice) even on max settings (apart from when the alloy turbo boost stops in MP... )

My thoughts on this. Note that this isn't a 'do all of this', but just some ideas on 'fixing' mid-late game economy.

- Change Trade Ports to be 6 or even 8 logistics slots each. They're just way too 'strong' for how little of a footprint they have. Compare how effective just one trade port is, versus generally needing at least two orbital refinery structures to get any meaningful income from them. Addicionally, have any of you seen a planet with one or two +trade% bonuses, with five trade ports? I had one planet making around 50% of my total income!

- Remember the 'High Security Protocol' bonus? What if the more tactical structures you had, the less effective trade would be? Somehow I doubt traders would be happy about traversing a mine field just to drop off a load of bobblehead dolls.

- Destroying multiple trade / refinery ships along a route will 'disable' that route for a period of time, or at least limit it. For a period of time after cessation of attacks, no ships will utilize that route, with the resulting long-term impact on the economy in question.