I'm not sure what your point is. Do you think the small population on the island should have to pay for all of it?

The French-side Collectivité is technically an EU territory, although not part of Schengen. The Dutch side, as a separate country, is not part of the EU, although it is a constituent part of the Kingdom of the Netherlands. The Recovery Trust Fund, which sponsored the clean-up on the Dutch side of the island, was significantly funded (€4.70M) by the Dutch government, so not dissimilar.

The funding by the EU is a fairly common practice under EU disaster-relief programs. Thus the €4.28M from the EU, €828K from (I assume French) State credits and €444K from the French Collectivité itself is not unusual. I'm just glad it is finally getting done.