Buy Rtx 2080 or Rtx 3080

So in my Region there are 2 Haus that interest me used

Rtx 2080 for 170€ ~ 180€

And rtx 3080 for 320€ ~ 340€

I know that the rtx is around 30% ~ 40% better than an rtx 2080.

But i dont know if its worth to pay 140€ more for only around 35% more fps. If i add another 40€ i could by 2 x rtx 2080 with it.

I only play cs2 and singleplayer games from 2020 and earlier (backlog).

Help me decide with good Argumentation.