I have made it free at times, but that hasn't seemed to pay off in terms of the additional IAPs. I don't usually do 99¢, on the theory that anyone willing to pay $1 will be willing to pay $2. Sometimes it is as much as $4.99.
I'm curious to know how often others change the price of their apps, why they change the price (seasonality, experimentation, to get flagged by "sale" aggregator websites that notice price drops), and how it has worked out for them.
https://apps.apple.com/us/app/beeline-reader/id938026867