If a game that I initially purchased becomes free...

[BlueScreen92jrd]

...then what do I do?

I have purchased a copy of Super Bomberman R Online for around $10, but now that Stadia has this game as a free option, what can I do to move the funds back to my Google Play account to purchase another Stadia game?

[Juxpitos]

If they are like xbox, you won't get a refund unless you purchased the game a day or two before it went free. Best bet is contact support about it and see what they say, if you've had it for a while I doubt they will refund it.

[BlueMarble]

That is a bummer.

If bomberman is a stadia pro game, your purchase would still retain some value by being able to play without subscription.

But since it went completely free for everyone, I feel your pain. Hope Stadia will give you some sort of Stadia game credit.

[Tobonaut]

Hi @BlueScreen92jrd 

that could always happen. Just appreciate the time you spent before it was free. It seems that the game was worth for you.

[RXShorty]

There isn't much you can do about it I am afraid.

But the version you bought gave some extra's characters right?
It seems that you bought the Premium edition, the Free edition is missing characters and such. 
So it shouldn't be "total waste"