I don't see dive prices reducing, everyone has their hand out and see the dive shops as cash cows. Fuel is now around $25 MXN a liter and because PEMEX is losing about $11B USD a year and $100B USD in debt, it just keeps going up. The city now controls the marina and with its bloated work force it is proposing a 4-5X increase in slip fees, with the latest increase park fees are up about 5X over about 3 years. The taxi's are now demanding 3X the official rate to get to the marina and the taxi police only make sure there is no independent competition to the Taxi mafia, but wouldn't dream of making their relatives follow the official rate card.. I also hear more and more stories of criminal groups trying to extort local businesses and it is only a matter of time before they get imbedded into the centro district.
So in a nutshell I do not see any price improvement coming on dive prices.