Forming an association of professionals can't do any harm but, I doubt that you'll ever have any success at standardizing pricing without either 1) unionizing the trade or 2) getting the government further involved. I don't like either idea and I don't think there is a viable solution to getting rid of lowball pricing. As someone who provides both tree care and stump grinding services, I believe the main problem facing the stump grinding industry is simply that stump grinding is not a highly technical trade. Most any homeowner can rent a small stump grinder and do the work him or herself with a relatively small learning curve. Unless a removal job requires a specialty machine which can't be obtained through a rental store, we, as stump grinding professionals, are simply offering our clients the convenience of not having to rent the machine and do it themselves. Many of those homeowners have realized how easy it is to do and have purchased their own machines with the intention of making a few side bucks or, in some cases, to dream of getting rich my going into the trade full-time.
I don't mean to offend anyone on this site but, the simple truth is that stump grinding is a very basic blue collar profession. I do both white collar and blue collar work and I have no problem with either type. I'm simply saying that stump grinding requires very little training or experience to break into. It's a profession where having little or no practical experience is not a problem so long as you have $5-10k to buy a used grinder. Stump grinding is just not that hard to do and, so long as machines are plentiful, it will never bring the bread and butter that specialized tree care services have the potential to bring - especially during tough economic times where so many people are looking for side jobs to bring in extra money.
Look at the guys who are still trying to make a living by offering just skid steer services and nothing else. Twenty years ago, before every contractor and farmer owned one, a guy with a 643b bobcat could actually make a living just by sitting in the seat of his loader and leveling dirt or drilling post holes all day. That's all he had to do - sit on his butt and move some dirt or clean out a livestock barn. Now, anyone can get his hands on a skid steer and do the work himself so long as it's not real technical in nature. The machines are getting easier and easier to operate. The same goes for stump grinders.
Time will never go backwards. Stump grinding is not what it was 20 years ago and it never will be again. It's time to deal with the changing times and either accept it for what it is or find another trade to get into. Neither certification nor membership to the NSRA is going to bring back the yesteryears.