With the original price as $250, a 100% increase would be adding the entire value to itself once (i.e doubling) taking us to $500.

A 200% increase is adding the $250 to the original two times for a total of $750.

So calling it a "200% increase" is correct.

It is true to say that "$750 is 300% of $250" or that "The price has tripled" - both correct, but the increase is only 200% because increase doesn't include the original as part of the value.