Beetoothven is one of the two skins released in the first part of the Mr. Spank's Beats Shop offer. It could be purchased as part of an item deal in early November 2018.
Beetoothven could be purchased for $9.99 in the limited time "Best Deal!" which included 25000 coins, 1200 DNA and the Tape Guy skin. This skin was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: The first part of the Mr. Spank's Beats Shop offer was released again for a limited time in late January to early February 2020. The price and included items remained the same for Beetoothven. However, the amount of coins and DNA were reduced to 12000 and 800 respectively.