Both of the add-ons that you've listed can be purchased through the Atlassian Marketplace. However, prior to being sold, they were offered as free add-ons.
The Marketplace view in your JIRA instance is tailored to your personal JIRA version; in other words, only add-ons compatible with your JIRA version will be displayed. I'm not sure what JIRA version you're running, but it is entirely possible that the latest *compatible* add-on versions are free whereas the newer paid versions are only compatible with newer JIRA versions.
Feel free to file a ticket in the UPM project if you think something else is going on and we'll take a look.
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