Should be said you don't actually need an agent, at least not if you're from Thailand since Taobao actually covers that region, that being said, if you want to contact the seller you either need to speak Chinese, or know someone that does, since most taobao sellers will not know how to speak English, which is where most agents come in, they give points on how taobao works (taobao rating system is hilarious), handle shipping which may be required for certain countries, and they handle communication between the buyer and seller, they may also provide some alternative payment methods like paypal and what not, although that is of little use since taobao is really like ebay, except a lot bigger.
For anyone thinking of ordering from taobao it isn't just the Price + P&P that needs to be considered, since this is the sort of item that will very likely be stopped at customs, so in all likely the price would be the price of (the seller + P&P) + vat (over the declared price) + any customs fees.
P.S. Not actually correcting you, just clarifying things for people that don't know what taobao is.
Also not sure if you are aware of this, but you would very likely need to add your region VAT to that price too, plus some fees, since this product would almost certainly be stopped at customs and get taxed.
Not sure if this applies to all agents (there are many!) but the one I use automates the entire process. I submit the link of the item I want, pay up (this would be the cost of the item as listed on the Taobao seller's page) and wait. About 10 days later I receive an email telling me the item is ready for delivery / collection plus an invoice for everything else I owe. This would include the international shipping fee, import tax if appliable (there is a decent tax free threshold) as well as the agent fee. Once I pay the item is then released for delivery / collection (in this case I chose collection since it was too large for delivery).
When everything was done and dusted I paid slightly less than US$1,000 for the monitor, which I think is a very fair price considering it includes shipping, agent fees and taxes.