The amount inferred by the term may vary for all of us but it’s a huge amount of money for someone who is referring it in a particular situation. If we take the term literally then considering the 1000 Rupee notes, which weigh around 1.2 gram each, a ton of money will be nearly Rs. 83,33,33,333.33.
The lawsuit cost the company a ton of money. It implies that the company spent a significant amount of money on the lawsuit. The exact definite amount may be large for this company but for some other company it may be comparatively small amount.