Is it possible for me to get the refunded sale amount?

I think its a bit unfair that I paid full price just a week ago now I find I could've waited a week and got 80% off. GOG should show which games they plan to put on sale or at the very least refund the extra.

Nope, that’s not the way commerce works. No one knows what is going to happen in the future, you agreed to pay the cost at the time you wanted it, end of deal. If they come back the day after you get a discount and double the price, will you be jumping in to pay extra?

Edit: that being said, GOG are generally good with refunds, but you would need to put in a support ticket, no one here can help.

1. Go to your orders and click the Ask for refund link next to the game(s) in question.
2. The game being on sale is the first reason listed on the form. Presumably that means it's a valid reason, though "I didn't like the game" is also listed.
3. Choose to receive GOG wallet funds, so you only have to wait about 24 hours. You can use wallet funds on their own to buy other games (or the same games), or combine with another payment method.

Further reading: How do I refund a game?

This was always my thought. "They should refund me the extra."
If you bought it right before an unannounced price increase, is it fair for them to charge you the difference? It's plenty fair that Johnson444 paid full price a week ago, and doesn't get the discount now. However, GOG are generally a good company when they don't have their head up their own ass, and they will refund the difference most of the time.

I agree with you 100% on this one.

As the current rules stand, you can ask for a refund within 30 days of purchase, no real reason required I think ... never done it myself, but that is what I have read.

It would be a risk maybe, but you could meanwhile gift a new purchase of the trilogy to yourself, and then Redeem the code after you get your refund.

EDIT
Ice_Mage lists what seems to be a better solution, without risk.

If you follow the steps Ice_Mage kindly provided I'm sure you'll get the difference back.
But, there's nothing unfair about you having paid full price. Why should they disclose sale dates? Do you see Steam do that? Do you see any company do that?

you should never ever buy any game, because at some point they may be sold cheaper

The same goes for groceries.

Thanks, I just did it, and no I didn't know about this. GOG really are a great company to allow this. I will spend my refunded money on Two Worlds 2 discount.

Good choice. Two Worlds II is a pretty good mostly open world RPG with beautiful vistas and plenty of orcs to play with (they're the good guys for a change) as well as plots to unravel and secret dungeons to delve.

Thank you for the explanation. I didn't know this exact option.

If you choose that option number one – does it mean that there's an option to just take a difference to your GOG wallet and keep the game in your library? Because it won't be always possible to re-purchase the game before the sale ends.

I believe all refunds are full and result in the game(s) being removed from your library. I think "reason" is part of the refund form just to weed out refund requests for games played in full, and for GOG's analytics. I'm not aware of any partial refund scheme. In theory, support might help with this, but getting a response takes weeks, so it's not useful if you're looking to buy something on sale.

I got this impression based on the refund form you get when clicking "Ask for a refund" and the aforementioned support article. I've never requested a refund.

Nope, you'll have to wait till refund finishes, and only then buy the game again.
Allegedly it takes about a day for wallet refund to come through, but my recent experience shown that sometimes it might be days before your wallet refund is even acknowledged via appropriate mail, and then it gets shunted off to human support which took about a week to see and approve it - I still managed to rebuy what I wanted, and I suspect it was some error and not a standard of how things would be from now on, but still something you should be aware of and a risk you'd have to accept if you request a refund with the intent to buy the game cheaper.

I've done this about 2 times so far. As Ice Mage said:

1) It is a valid reason and yes, it is literally the first option you can choose from the list.
2) it is quite easy and quick IF you go for wallet funds. Those get processed within a few days max (usually within 24-36 hours). The game gets removed from your library, price gets added to your wallet funds and you can immediately rebuy the game on sale.

But if you want it to be done quick, do choose wallet funds. Full refunds can take a month to process and you will most likely miss the sale you are refunding the game for.

In this case, if you can afford it, but the game as a gift before the discount ends, then redeem the code after the refund hits your account and the game is removed.