IMHO, because "whale" is a top, highest level, the barrier for it should be set accordingly. As it is in steem.
Whale is the largest animal on this planet, hence this title got to be used properly.
There is no such thing as "whales for poor people in Africa", and "whales for USA millionaires". Whale is a whale. Whale's size always calls for respect.
500 Steem does not seem to me to be a right level, in any environment, no matter how poor or rich it is.
One month ago I was in Madagascar, a country in the TOP10 of the poorest in the world, and even there I noticed some super luxurious cars, which I would not afford in my lifetime.
Myself I live not in a rich country, and €100 (500Steem) is a ~1/3 of my monthly state pension.
Nevertheless, I would not call anyone a "whale" in any SCOT tribe, unless his total stake of that particular token is equivalent to 10K of Steem, or more.
But this is just my personal, subjective opinion.