i have 3 good used back boxes here £20 each
a good used midpipe usually goes for £100 due the the value of the cat - i paid £175 for a stainless mk2 decat pipe for my car - which is essentially a bit of bent pipe , so your €60 quote seems alright
i also have a very nice a superduper rare japanese FGK stainless backbox aswell , but its £300 ( no midpipe included) and its guaranteed to make you much more manly and surprisingly it will make you much more popular with the opposite sex! apparently it adds 4 inches in girth to your private parts
or you could try ebay

and im still totally unsure as to which part of the exhaust it is that you need....backbox or midpipe ..christ on a bike,,,this hurts my head