Well, like often happens, Google couldn't fix this and is still looking into it, but XDA Developers had the answer.

If you have a beta key, or have purchased the key and keep getting a notice when you try to install/update that you can't install it because you haven't purchased it, follow these instructions.


http://forum.xda-developers.com/show...1382598&page=2

I found a simple solution in http://forum.xda-developers.com/show...4&postcount=18 but it had German instructions which I followed as best as I could and was finally able to purchase Tunein Radio Pro from the Google market.
I used Firefox and new Google Play market.
Basically you go to the Google market website on your computer and RIGHT click on the "Purchased" button - that.s the same button that you would normally Buy/Install an app.
When the menu shows up I chose "Inspect Element" which added a menu bar at the bottom after pressing HTML button on the right my browser was split in two with the bottom now having the source code of the "Purchase button"
Clicking "Purchased" in the upper window highlights the code that is executed. In my case I had to scroll a few lines up and found the beginning of the line with "<a class="buy-link buy-button goog-inline-block", and in that line I found data-ispurchased="true".
Double clicking on just "true" opened a pop up window where I could change the value to false.
Clicked on an X on the right in the menu that's between my two window panes closing the bottom Inspect pane.
Now LEFT (normal) clicking on the "Purchased" button allowed me to buy the app.
Though in my case, it still said "INSTALLED" for the button after I hit X, I clicked on it and I FINALLY got to fully purchase the key. You'll know the purchase actually went through if you get an email.

I posted about this in the old Support Forum format, thought I'd share the answer. Seems this happens to a small subset of folks purchasing apps.