I think it varies. Obviously the risk is why there exists such a markup. Selling home made T-shirts doesn't run you the risk of going to prison. If the grower deals with only a small group of people that they trust, it will be more secure for them and they can lower the costs as it is lowering the risk. However dealing large quantities of any illegal product risks lengthy prison terms and the risk should be reflected in the reward and the grower only has to make a few large sales. However the dealer can minimize their risk by dealing to a small and trusted clientele and also minimize the risk which can lower the price.
If I was to deal, I would prefer to only deal amongst a few friends and in larger quantities so that I could sell to people I trust and not have to worry about getting ripped off or arrested by law enforcement as I would trust my customers. If however I was dealing and unable to do so, if I had to deal with strangers and worry about being ripped off or arrested because I did not have a good clientele that I could deal to exclusively, than I would want more money as I am risking more. Especially if I am dealing in smaller quantities.
If I was growing and had to deal with strangers, I would be very hesitant to deal with strangers and in large quantities that a grower will typically sell. It makes much more sense for me to sell a few pounds to one or two people I trust than start making smaller deals with quantities that will put me in prison for the same amount of time. If one criminal charge for dealing a pound of weed is the same charge I would face for dealing an ounce, than I would rather lower my risk and get rid of it in one deal. Safer for me in the longrun, especially if I trust the person.
In a state with Medical Marijuana, I would much prefer to sell to a dispensary as I would feel more comfortable selling to a business then meeting someone somewhere.
Either way the market will set the value, and I don't think it is greedy to markup a product so much if people are willing to pay. Weed is not something that a person needs or they will die without it. It is not food, air, shelter, or even a medical treatment. If it is so important that someone demands a better price, tell them to grown their own and to deal with it. Everyone involved takes a risk and it is up to them to set the price for that risk. Any sort of criminal enterprise boils down to eliminating the risks. Growing one plant is much easier and safer than 100 plants. But the reward is not nearly the same.
So for those who think the dealer should make more, why? If they only sell to one person who deals it out, then the risk is minimal? They worry about having it in their possession as they will have the plants longer, well if they are smart and only let a minimal amount of people know they grow, then the risk goes down dramatically. And if the dealer minimizes the risk and only sells to a small group of folks, then it will lower his or her risk and they don't have to worry as much.