When you are working with major retailers than you will definitely have to pay them a percentage of the money that you make once you start to sell eBooks online. The major retailers usually require their e-Books to be priced under the $10 mark so that you can get the highest possible royalty rate which is usually somewhere between 65%-70%. If you price your book anything over this price, then those royalties can drop significantly all the way down to only 30%. Another thing is that sometimes you will be required to wait in order to get paid. Payment terms vary depending on the retailer and in some cases you may have to wait weeks, or even months before you actually get paid.
Using a retailer in the ranks of Amazon or Apple definitely has its benefits. However, there are definitely cons there as well and any one of those cons may be just the thing that stops you from selling your eBook. With all of this information in front of you, it is up to you to decide if retailers are the way to go, or if being a self-published author will be better once you start to sell eBooks.