Here we go again...
There are lots of sources out there, and this is an extremely competitive business. I keep a small database of vendors in an Excel spreadsheet, including feeder types, sizes, quantities, prices, & shipping. IME, prices can vary quite a bit with supply & demand, so when it's time to order, it doesn't take long to go through the list and find the best deal at the time of order. This usually saves us between $10-$20 per order, but that of course will vary on the amounts & types of feeders you need.