The price point is for the first year of Disney+, after which the price will increase to the regular amount of $69.99.
The offer (found here) is available to households in the U.S. and Puerto Rico on Cyber Monday.
For the breakdown on what that seemingly arbitrary number means, that’s actually a markdown of $10 bucks on the annual cost, which may not seem like a lot, but given the service is already not super expensive, that’s a big markdown, particularly percentage-wise.