I'm aware that the cost in troops or goods can be prohibitive for some cities. Like I said though you need to develop your city in a manner that will let you do GE4 without it being a 'break the bank' situation whether it be goods or troops. I'm guessing you auto battle? Manual battling takes time but you can generally be much more effective running your troops then the computer which would make the battle less costly. If nothing else when you mess it up you can retreat before losing all of your troops thus limiting your losses.I like the prizes that are good. I don't like it when the claw comes up empty handed or gives out coins / productions. I'm burning tons of goods and troops. By level 3 I'm burning 5 goods per negotiator...and up to 7 from what I've seen in level 4. That's 35 goods per try and with at minimum 4 tries, that's 140 goods per encounter. Even more if you need more turns and don't want to pony up 10 diamonds for yet another 35 good turn. Then multiply that by 12 encounters per level. That a lot of goods or troops to burn up for a chance at prizes like houses & decorations, I think in the end I would like the coins and productions to be replaced by a chance at expansion, medals or even next era goods that would be great for getting ready to level up.
If you are going to negotiate then you'll need to concentrate on goods production whether it be the Chateau (as someone else mentioned) special buildings or goods production buildings (or any other method I may of left out). Figuring out what to develop in your city to improve the outcome (in terms of troop lost or good cost to your overall production) is an important function to being able to get those rewards consistently and at a price that is manageable. What troops are you using? Picking the right troop (whether manually battling or auto) is important to the outcomes.
Have you gotten any higher aged troops from the continent map? Those can be quite useful for GE if used properly.