Actually, the bonus will range from almost 0 (if players simply "don't play" the tournament) to 50, if they perform twice as well as expected.
If you've noticed, the leaders' results are almost always the same (fluctuations are around 1/10 of the total rating). In the grand scheme of things, this isn't too important.
Wouldn't you want fewer tournaments to always award more points than more tournaments?
If you want to "hold back" the leaders, then the final effective rating should take into account its average value. Or you could limit the number of tournaments per year, for example, to 12. If they play more, they choose the best results. But is that necessary?
Although you should understand that the additive nature of the rating hides unpleasant and inevitable pitfalls.