Learning how to sell

One of paradoxes of my life is that on the one hand I'm anti-consumerism and the constant accumulation of possessions and on the other hand I own a shop and I want it to sell more goods. In fact I'm currently at a convention with a focus on growing the industry by persuading people to buy more. I justify this by thinking of the good that can be achieved a) by the projects we sell and b) by the projects we as a business are committed to. So here's the thing, recognising business as a legitimate enterprise, recognising the buying and selling of goods as a legitimate enterprise what I'm left with is where's the line?

It's too easy to become judgmental about all this but at some point we sacrificed generosity to others for selfish reasons or gain but at what point? How would you recognise it if you came to it?

So if there is anyone reading this, here's the question? How much is too much? Or perhaps better still, what moment in your life made you think, 'this is crazy something has to change'?