I use a postage scale too. I also bought it off of ebay. My standard shipping rate is $5.95 for just about everything. It covers the shipping and supplies 95% of the time. If I have something very heavy, I will weigh it and do the postage calculator plus add $2 for supplies and to give myself a small cushion in case I screwed it up. Sometimes, I get caught with a package that will cost me more than what I charged but for the most part, I normally make about a $1 on each transaction.