So, I decided to throw many money at gog.
Problem is that lots of games were having good discounts during the summer sale, so I'm hesitant now to buy them full price...
I could wait, but I want to throw money now. Alternatively, I could buy games that weren't discounted big during the sale, so I don't feel bad.

Just wait until the next sale, there are always half a dozen ongoing and a big one every couple of months, plus odd ones here and there etc. No need at all to buy anything full price, that’s the sale culture now in force.

You could try buying games that are on sale now, like Fell Seal: Arbiter's Mark.

(The DLC for the game was just released, so it hasn't had a chance to go on sale *yet*.)

(By the way, I am considering getting this game.)

If you just want to throw some money, I could offer to try and catch it. ;)

Seriously though, if it's about specific games you want, why didn't you buy them during the sale? And if it's just about supporting GOG by spending money on random games, why does it matter what discount they had before? Why do you feel you want to buy the games now? Do you actually intend to play them right away? Did you already play or at least try all games you've bought in the past? Just a few questions that might help you to put things into perspective (or not).

That being said, I didn't even perceive the sale as a big thing. GOG is doing so many of them these days and always with more or less the same discounts, no real suprises, no real bargains anymore. The next one is probably just around the corner.

Most games are on sale regularly. There are a few outliers which can go years without being on sale, but those are few and far between.

As nightcrawler said, there is pretty much no reason to pay full price these days.

How about purchasing some GOG wallet funds? You'll satisfy your immediate desire to "throw money now" while ensuring you have funds waiting for the next big sale.