Every craftsperson depends on a wide range of suppliers to obtain the necessary materials and supplies to produce the work. Some are more important than others, and likewise, materials are more important in some craft media than others. A jeweler specializing in gold and diamond rings places more emphasis on her supplier relationships than, say, a potter. It’s just common sense: (a)diamonds cost more than mud, and (2) the diamond as-purchased is an integral component of the finished piece, while that one-of-a-kind vessel bears little resemblance to the mud it started as.
There are two rules-of-thumb to keep in mind when dealing with suppliers. First, try never to let yourself be caught in a situation where you are sole-sourced by one vendor. If you have only one vendor from which to purchase your findings or materials, then you have a major exposure. Your supplier may be out of stock. He may raise prices on you with impunity. He can jerk you around on delivery or credit terms and there is nothing you can do about it, because you have to buy from him. Always try to have at least two suppliers for critical components. Then you can jerk them around. Try playing them off against each other. You will be surprised at what can happen to the price you pay, the delivery times and the credit terms IF Supplier A knows that you are also talking to Supplier B.
The second is that you should always be trying to get past your supplier to deal directly with his supplier. Why? He’s making a pretty good living sourcing your needs and those of your competitors, isn’t he? How would you like to put his profits in your own pocket? Sure, you might have to buy in larger quantities, and money is always tight, but for stock materials with a long shelf life there are significant economies of scale in buying in larger volumes. Many craft materials go through several hands before they reach the actual maker, and every one of those people is making a living. Shorten the distribution chain. Ideally you could combine these two rules by purchasing directly from two different manufacturers. There are no middlemen, and both are eager to get your business.