Most wholesale sites require you to set up an account before they show you their actual wholesale prices. So it's possible you are actually viewing their retail prices. It doesn't make sense that retail prices would be lower than wholesale, but without knowing specifically what you are looking at, I can only guess.
In regards to the legality of relabeling and reselling retail goods, it really depends on what shirts you're talking about. Based on the "first sale doctrine," once you buy something at retail, it is yours and you can do what you want with it. But buying a Nike shirt and relabeling it for resale could be seen as a form of counterfeiting. So there are some fine lines to work out. Maybe you can give an example of what shirts you plan on buying for relabel and resale.
In regards to the legality of relabeling and reselling retail goods, it really depends on what shirts you're talking about. Based on the "first sale doctrine," once you buy something at retail, it is yours and you can do what you want with it. But buying a Nike shirt and relabeling it for resale could be seen as a form of counterfeiting. So there are some fine lines to work out. Maybe you can give an example of what shirts you plan on buying for relabel and resale.