Walmart offers the Fisher-Price Superstar Step 'N Play Piano, model no. V4357, for $79 with free shipping. Excluding the mention below, that's the lowest total price we could find by $19, although it was $4 less last fall. It features a rotating seat, glider rails for walking, piano keys, and a variety of interactive extensions. Three C batteries are required (not included).
A close price: Target charges $79.99 with free shipping.