I'm going to use random numbers in this example, so they're not necessarily the numbers you'll see when actually doing it, but the concept is the same:
If my partner has spent 30kp and gotten a chest that refunds them 5kp, they've spent 25kp. If I've spent 30kp and gotten a chest that refunds me 25kp, I've spent 5kp. Not hard to see I've gotten the better end of that deal, lol! Since many times the AW of the partner is one I don't have/won't ever build (exactly how it is right now!) or vice versa, I don't count runes. I consider them the 'free' stuff.
I'd give the extra 20kp to my partner; I'm not interested in profiting off FS members. If it wouldn't mess up the NetZero swap, I'd do it in that same wonder; if it would, I'll toss it in whichever one they want to use next and we'll both make a note of it so it doesn't interfere with us settling up the next time.
This likely only becomes a problem when you play with other nerds who pay attention to numbers, lol! Most casual players don't see it that way (the same reason why they think swap threads are fine and can't wrap their heads around NetZero) because they're not looking at numbers, they're playing the game and view folks who see the numbers as a bit obsessive/compulsive (they're not necessarily wrong about that!)
I see very little issues with players in my casual FS where we use swap threads until someone mistakenly skips a player and it doesn't get caught until several other folks have used the same swap thread and then I start getting pms. Gets real fun when someone noticed the issue a few posts back in the thread and tried to 'correct' it and ended up shorting someone else.
I don't use the swap threads personally, so I can give the smaller cities a better chance at getting some of those higher chests with higher kp chests and runes they may actually need that I don't! I have way more excess kp to throw around than smaller cities and with my
hoarding inventory could contribute to all the swap threads 1-2x's/day, total in swaps=180kp, so 180-360kp/day. Since I'm taking a break from the research tree atm, it could continue until I go into the next chapter in a year or so. Pretty much guarantees I and the other larger cities will take those top chests every.single.time. That gives us bigger refunds on our kp spent and runes we don't even need and keeps them from our mates who need them.