What's happening here is a normal part of market participation. It's not unusual to try and change prices to optimize sales and product market fit. Additional

What's happening here is a normal part of market participation. It's not unusual to try and change prices to optimize sales and product market fit. Additionally, you don't necessarily know what the customer is thinking. For example, some of the lifetime purchases I've made are because I see a deal as well as a desire to support the person building the product. To be fair I do usually see the prices increase over time, so I understand your concern. Even so, I don't think you should worry about this or take any pro-active action. It's your right to adjust pricing as you see fit. If it bothers you, have a plan in reserve to provide a partial refund if any customer asks what is happening. The reality is very few people will probably even notice.