What would you have done in this instance?
Minded my own business. It wasn't your conversation and you simply butted in where you weren't wanted. A little common sense would tell anyone that a "pro" shop is going to be more expensive than a mass merchandising box store, even where sporting goods are sold. If the "customer" you chased away wanted to make a purchase without a busy body butting in, he/she should have been allowed to do so, even if it meant spending an additional $125.
Being in the IT world, I have tripped up many a BestBuy employee by telling the customer to purchase the fastest computer they can afford at the time because the faster model will do everything the slower one can—only faster.
Is this some sort of hobby of yours?