These cost far less to maintain than having a team or two dedicated to upkeep for the trees.
That said, these things are a terrible idea, clearly the brainchild of clueless techbros, and overall a massive eyesore. Trees are objectively the better option. Just not Bradford Pear trees... Anything but the cum tree.
These probably require more maintenance and not less, glass needs to be regularly cleaned and water changed and fertilized, what will happen when company stops supporting this proprietary algae aquariums?
The "cost" of maintaining trees is paid by the city to people living, buying things and paying taxes in the city.
People who don't have a college education and get to make a living working outside, improving their neighborhood.
The fake trees are likely put up and maintained by a tech corporation from out of state.