Replying here with the data about "the worth of its size":

-- the very numbers reported here introductorily estimate a maximum of 80,000 capacity for the Colusseum, and

-- a search for "size of stadiums" shows that the Wikipedia page starts listing from 40,000 - up to 100,000 to 132,000 for just a dozen constructions, and

-- the Colosseum was built between 72 and 80 AD.

This must give an idea of the actual worth of the endeavour.

There are plenty of other areas where size may actually matter, and Romans never complained.

it's a lot smaller in person than how big people think it is