Let's take an example - this whole Class 100 business. 100 tons sounds like a lot, right?
Take a room that measures 20' x 20' x 10'. Not so huge, eh? Fill it up with water. Congratulations, you have about 113 tons of water (metric tons, which are pretty close to Imperial tons).
Take a block of granite that measures roughly 10' x 10' x 13'. You now have about 100 tons of rock.
Block of iron 6.5' x 6.5' x 11' or so, and you've got over 100 tons of iron.
The Mutants and Masterminds RPG used to have a table of weights, using stuff to give examples. The masses of nuclear subs, battleships, aircraft carriers are astounding - orders of magnitude above 100 tons.
747 jets - EMPTY - mass somewhere between 150 and 220 tons depending on the model, and some 'Class 100' (or less!) comic book characters throw them around like spears. ^_^