Oh, it's immensely massive compared to anything that's likely to possibly exist as an element. But in proving something is finite, it doesn't matter if we overshoot by a million million percent, all we have to do is establish any bound at all. We don't have to engage with the question of what we can do in a lab, because the question only requires any theoretical limit to exist.

It may be difficult to predict just how far we can go in a lab, but the existence of black holes means there must be some limit.