In short, no, it isn't.
Instagramer costs $71 monthly per Zendesk Instance (subdomain, not agents). For this price you can connect all your Zendesk agents to enjoy all the advantages of this app, working with Instagram direct messages faster and more effectively. Besides, there's an opportunity to connect up to 4 Instagram accounts to a single Zendesk Instance without any additional fees.
If you need more additional IG accounts (5 and above), it will cost $18 each.
You can also use our free trial for two weeks and see all the pros from inside. To use a free trial you should install Instagramer from the Marketplace. When you install the application, you will still be asked to enter your card details - this is a Marketplace requirement, but no charges occur until the 14-days trial period ends.
If you want to install the app, please follow this article: How to create a Zendesk integration with Instagram DM?
If you want to avoid charges after the end of your free 14th-day trial, you need to uninstall the application before the trial period ends as described here: How to uninstall an application and cancel its subscription.