Just a quick tip with suppliers, don't take any advertised price as fact, especially with wholesale. So wholesale suppliers will be selling public direct, but still offer a good wholesale margin on their products. They won't be advertising that price up front because most of time it will come down to what size volume you will be purchasing in.
So it's always worth at least having the conversation with them to confirm.
In regards to genuine wholesale margins, this really comes down to the type of product and the market itself. I know of an electrical retailer who spends upwards of 150,000 AUD per month on stock and they have a margin of 7.5%. The trick there is turnover, when you are moving upwards of 150,000 of stock per month, 7.5% is a nice little earner.
One of the biggest margins in the market is in food, especially in things like coffee. That's at the retail end, not the wholesale end. Retail coffee has around a 400% margin in most cases, that's barista style coffee I mean. So any one thinking about going into the food business, you can do a lot worse that make sure you get a coffee machine :)