I think 50 is even a large number. YC's real value to investors is selectivity. As long YC maintains that brand, investors will continue to have a YC-biased perception making it easier for these startups to raise funding. The same selectivity makes getting into YC enticing as it validates them and their ideas. I'm sure the reason behind the cutback has been scalability ( I made that comment before and it made PG defensive a bit) however, the move ensures the longevity of YC's mystique.