>>2722378Good quality sleeping bags usually cost between 250-1000, really depends on the amount of fill, fill power, material, brand etc, Granted you there are down sleeping bags for 100€, but I dont know about the quality, you xan always buy second hand.
Synthetic bags are also an option, since theyre much cheaper and condensation doesnt affect them much. Decathlon also carries them, they cost around 60-80€, but the 0C synthetic one weighs twice as much and isnt nearly as compressible