To charge more you need to convey more value. Let’s be honest, it’s probably very much a concern of yours that you will lose some paying customers. It reminds me of an old consulting joke about a barber. Consultant is getting a haircut and says “you should double your rates” The barber says “double my rates?! I’d lose half my clients!”

Understanding the value you provide and the clients that get the most value from it will help you differentiate yourself from others offering a similar service.

By thinking from your customers point of view you can understand the value that they get from the website and double down on that. You could even survey a portion of your most profitable clients and ask them what’s important to them. Then focus on improving that aspect of the site.

Hope that helps! If you have a strong niche, a strong value proposition and provide more perceived value with your updates then you could probably charge more than you’d think.