Amazon has Classic Rock 'Em Sock 'Em Robots Arena Playset (Mattel Games) on sale for $9.99. Shipping is free w/ Prime or on $35+ orders.

Alternatively, Target also has Classic Rock 'Em Sock 'Em Robots Arena Playset (Mattel Games) on sale for $9.99. Select free store pickup where stock permits, otherwise, free shipping on orders $35+

Thanks to Deal Hunter phoinix for finding this deal

Note, product must be sold/shipped by Amazon or Target respectively