The price should depend on what the perceived value of the freemium product vs the perceived value of the top-line product.
I keep saying perceived because it is important for you to know what the customer values. If the freemium product offers all the services at a basic level, would the customer want to go above the basic level and pay for additional services? And if so, how much would the customer pay?
A classic example is Winrar. Everyone uses the free version, but no one I know bought the paid version. In my opinion, I believe that winrar gave away too much for free and the perceived value of the paid version is too low to justify purchase.
However, by allowing customers to pay for selected additional services, you open up options for your customers and increase your own revenue options as well.
My personal opinion is that if freemium + all service bought = X price, the premium service should be less than X price. This is if the freemium version with full upgrades has the same offerings as the premium service.