If you already have a reservation.... on the website click “My Disney Experience” at the top right then click “My MagicBands and Cards”
There you’ll see your resort reservation. Click “Get Started” and it’ll take you through the process of selecting bands where you can see the various prices for what is currently available. You don’t have to finish the order if you just want to poke around and see prices/options.
It is correct that the basic color ones are $5 for 2021. Other options have various prices.