The king realized that few people would be able to check the results of his experiments. Few if any would have the resources he had at his disposal to duplicate his experiments (v. 12). Wisdom is better than folly in some respects, but neither provides a key to discovering net profit. Consequently Solomon concluded that being wise only has temporary and limited advantages over being foolish. Ultimately there is not much difference. Both the wise man and the fool die, and their survivors forget them.
"Grievous"(4:17, Heb. ra) is the opposite of "advantage"(1:3, profit). It is loss. The fact that Solomon could find nothing in work or pleasure that could yield anything ultimately profitable led him to view life itself as distasteful and repugnant (v. 17).31