MissMary has brought up an important point about the manufacturer's instructions. You mentioned the wax being able to hold 6%-10% FO. What about your FO? You need to pay attention to its recommended usage rate (either look on the bottle or ask the supplier) as well. My lavender FO from Peak, for example, says to use 1/4 - 1/2 oz per lb of wax, which translates into a maximum of 3%. So even though the wax could hold 6-10%, I will obey these instructions and use no more than 3%. If you're interested in buying in bulk to reduce your cost per candle, you could start with ingredients which don't expire, such as wax, wicks, jars. For ingredients which need to be fresh, such as FOs, you could figure out how much you need for 1 year and buy that quantity. If you're not using much of each scent, you could consider cutting back on the number of scents offered so that you can buy larger quantities of each FO.