This is the dilemma,I have an avanti carbonio half alloy/half carbon(sounds like a dog biscuit) that I paid $250 for and it was hardly used, 2007 model, 105 etc and FSA gossamer cranks.
Goes ok but my bianchi that the previous owner stumped up $8000+ for is far better...
8 grand better ? I am not so sure as a recreational rider but it sure feels much nicer and comes down to what you're willing to stump up or have expendable.
For me, $2000 was my max and I am happy with the 928SL but was just as happy to ride my $250 second hand oldie.
So there's certainly a high element of fashion and peer pressure from my mates as both of them that I ride with have probably $15000 in their 2 bikes between them but paid full retail (mad buggers) but both have $150,000 jobs.
Suppose it depends what you're happy with.