I have deliberately priced my product low, and now I wish that I hadn’t.

I priced myself low to reduce any friction for my initial customers, under the assumption that I would increase the price once I got traction. Now, after 18 months in business, I have 50 percent of my user base grandfathered into pricing that doesn't even pay for customer support.

How did you justify increasing prices for your customers without being perceived as doing a bait and switch?