Sorry if this doesn't make sense but I'm going to try and describe this as best as I can...
When you go online to the Chevrolet website and build a V6 camaro, the RS package option is priced as $1600, but if you build a V8 camaro, the RS package option is priced as $1300. So using that logic, if one were to select the 45th anniversary package, I would bet that suddenly the RS package would be listed at a reduced price below $1300. GM is smart about this stuff, they realize that people aren't going to want to pay for a package that offers stuff that's already on another package. Their thought process would probably be: "If we leave the price at 1300, no one will select it and we're going to lose that profit altogether, but if we lower the price, some people might select the RS package as well, and we get X amount of dollars instead of zero."