Chiming in to post on this.
My family and I were in Ushuaia on the 9th of March (Celebrity Eclipse) and set up a 2 part tour of Ushuaia with Mario Miraglia.
The Prices were 150 USD for the Tierra Del Fuego Park and 120 USD for the Escondido/Fagnano Lakes Tours.
He also took us around the city to various vantage points, took us to a gin distillery to sample local gin and to a fantastic all-you-can-eat grilled lamb lunch.
He was prompt, thoughtful and a great guide and was mindful of the mobility issues of one of my family.
Can't recommend enough, for a personalized experience in Ushuaia that was way less expensive than the shore excursion offerings from the Cruise ship.
