I use a number of suppliers, cheap as chips, I purchase and item from them for $10 and sell it for $20 plus shipping, sold 30 of them so far, about $300 profit, thank you very much.
Harvey Norman, geez, never thought I could make a profit from them, sold a dryer to a guy for over $500 plus $50 shipping, got it from HN for 350 plus $50 shipping, the guy lived 28 KMs away from the store delivering it.
Generally, if I sell something I google to see where I can get it cheaper..
HOUSE is another one, constantly sell an item for $7 which I get from house for $3.99
You never know what bargains there are.
Selling the PS3 items for $124, get them from Harveys for $88 but always haggle them, so far paid, $75, $85, $77 and again $77, these items are discontinued so I am thinking that my buyers cannot find them in stores, my local harveys only have 3 left, I will have to find more supplies.
I have also sourced product from Dick Smith
Just have a look around and see what you can find.
I have also just sold my last 10 litre urn, I purchased 12 of them, I made probably 30-35% profit on them, got one left which was damaged by aussie post, they paid for it but never asked for it to be returned, my gain.
Keep looking at other avenues for suppliers and hit the discount shops.