Nobody produces enough goods to trade as much, especially without using diamonds.
Just like nobody could beat 1750%. (psst - it's way easier to do more than 50 negotiations than it was to beat 1750%. I can do it without much planning for it at all - it just required one age up while leaving all my event buildings in the previous age). Once i've had sufficient time to plan, 100+ attrition negotiations may be feasible. Which is equivalent to 200+ fights - way past what's possible without siege camps (though the siege camps help both the fighting and negotiating options and unless the siege camps are close to 100% effect you're still wasting attrition by fighting instead of negotiating).
Food for thought:
A negotiation takes say ~10*the multiplier goods on average. A level 170 chateau makes 53 goods 5/14 times (I don't have one that high, but I could get one if I put the work in). or about 19 goods per quest. So if you need to negotiate at 20* multiplier, that's simply about 11 quests at 100 attrition. Now let's say you can do 4 quests per minute - that's 3 minutes at 100 attrition; not terribly different than a slow manual fight to win against 1750% boost defenses except that you're now at over twice the advances already by the time that comes up.
Now you might point out that you can't get previous goods from a chateau and you'd be right. But there isn't anything stopping you from building up a *huge* stockpile in your current age, and then simply stepping up an age (unless of course you're already in mars - but you can plan to do so for ceres). You could furthermore have a city full of good-producing event buildings left in the previous age to slow down how fast you run out your huge stockpile. As well as take advantage of trade to the extent possible to gain previous age goods (though assuming 1:2 as others have seems unlikely to me if you're going to try and make these trades in any sort of volume).
As such, 3 minutes per 100 attrition negotiation you want to do is in fact a reasonable supposition.
Edit: corrected math as dontwanna pointed out my mental arithmetic on how many goods a level 170 chateau puts out was wrong