Currently looking at implants, I need four, two either side bottom rear.
1000 Euro is cheap, if that includes implant and crown I would not hesitate especially at your age. Otherwise I gather that the surrounding teeth will move causing gaps, plus the lower tooth could grow up as it has nothing to grind against to stop it.
Hopefully some of the very helpful Dentists on the forum will comment, (and maybe do a deal on 4 for me!)