I need some evidence to back this up otherwise it actually is coincidence.
You don’t get very much gold for completing dungeons and raids as a guild.
The first guild I was ever in, the GM recruited only new players and dragged us through raids to get achievements even though we really didn’t know what we were doing. As soon as the guild turned level 25, he kicked us out. Went we to bed one night as guildees and woke up kicked. It seriously does help.
Cash Flow never took money from players.
It put a bonus into the guild bank, paid by Blizzard, which was based on what players earned as quest rewards.