You may be able to get a few more grams by using synthetic ferts (but then again, if you do organics right, you can usually get much more then you would with synth), but choosing to go organic is also about much more than just the final weight. It's about the taste, smell, potency, respect for Mother Earth, and unfortuantly, bragging rights, in a sense. Which brings me to your question about if people appricate buying weed that is organic, and I would say, absolutly yes.
I think people like to know that the product that they are buying is the best possible product that they can buy for their money. So if you sell them a product that is completely organic and let them know that, you will probably have returning customers, espically considering that there is a big "green" movement going on.
That is just my opinion.