If you don't log on several times per day, and thus cannot put in the time to farm the resources, or if you have maxed out on the allocation for the particular resource or resources, the building is actually quite helpful... So long as you have the money to invest as it is quite pricey in exchange for the return on your investment.
In my case, I have a 350+% bonus, and a 4 year built town, so similar to the others that make an exorbitant amount of in game currency, the investment is not going to put a dent in your bank. Under those circumstances, the building is actually a good investment to make up for not having the time to farm, or to create resources after reaching the maximum amount you can farm.