Humm...running the numbers:

Its 5 amb per 7 days for an advisor.
Each advisor gives +20% to a single luxary good and +5% to wood.
At $20 for 100 amb that means to hire all 4 advisors would be 20 amb a week or 5 weeks for $20. That's $4 a week.

Of course it'd only be logical to limit advisors to what goods you have meaning for the most part you'd only have 1 or 2 for your critcal goods.

Also on the boards they say you can hire 'merchants' for amb who will take a good and make a deal with it. Pretty much you pay to do what we do in the classified boards. You set X resource to the merchant and ask it to trade for Y at X:Y. It'll only deal in goods to goods instead of goods to gold like the trading post. Once all your resources are traded then the merchant departs and your amb is lost.

Seems like it'll be a system that will fail because of its system. If few people pay for merchants then there will be fewer merchants to trade with. Fewer merchants to trade with mean the odds of getting a good deal with your goods will decline. Bad odds of getting a good deal means few people will resort to them. Few people resorting to them means few people will pay for merchants.