First, attention: ISO 9001:2015 is not about product or processes, it is about the management system.
I belong to a group of people that think that value is not added to a product but something that emerges in the mind of a customer. Value is in the eyes of the beholder.
So, I made this figure to help me share how I see your challenge:
Your organization was certified and now wants to increase prices to previous customers because now it is certified. That is quadrant 1 on the figure, it is what I call arm wrestling. You cannot do it competition will not allow it.
Your organization was certified and now can access previous markets where ISO 9001 acts as an entry barrier. That is quadrant 2 on the figure, your organization has to find new customers that could value more your product and services.
Another alternative stands over developing a new offer, a new product, a better service, to the same or different customers, quadrants 3 and 4.