I was just reading a review (https://road.cc/content/review/257212-m ... isc-carbon) of this:
https://www.merlincycles.com/merlin-cor ... 27943.html (£1279)
This particular bike is bang-on trend having the supposed 'sweet spot' 2019 groupset, new R7020 105 hydraulic, though I think it doesn't like mudguards, which might well cancel out the supposed advantage of the discs.
The frame one presumes is straight out of a catalogue in Taiwan.
It's available on its own (with fork & headset) for £450 https://www.merlincycles.com/merlin-cor ... 06064.html (as an aside the wheels are £200 on their own, the groupset £650, the discs a whopping £80, and the other finishing bits about £80, so there's a reasonable saving for the compelte bike)
The review includes a few words about 'buzz', and this sort of damnation with faint praise
The Cordite's frameset is impressive. The overall quality looks and feels to be great, from the paint through to how it rides. Some cheaper carbon frames can feel 'plasticky' and resonate a huge amount, but while the Cordite does let some buzz through it is damping the majority. It feels like a really sorted aluminium alloy frame; if you've ridden some of the latest alloy offerings you'll know what I mean.
It seems that a higher quality alu disc brake frameset is around 1350 grams (e.g., Specialized Allez Sprint Disc), or Canyon Endurace Al. There are some lighter frames, such as the Emonda Alr, which is just 1112 grams, but I think this is at the extreme end of lightness.
A cheapo alu frame is more like 1550 grams. https://www.planetx.co.uk/i/q/FRPXRT58A ... d-frameset
Cheap carbon is e.g. 1.1kg https://www.planetx.co.uk/i/q/FRPXPCEVO ... o-frameset though the Merlin here is a bit higher spec at 1kg
Anyway, you are saving perhaps 500 grams for around another £300 on the cost of your bike. Which is about 60p/gram, and in that sense better value than say speccing Ultegra rather than 105 (200 grams for £200, more-or-less).
But is the alu frame better in other ways (durability, ride, etc.)? Conceptually there could be considered to be three choices here: 'cheap alu', 'cheap carbon' or 'good alu'. The good alu and the cheap carbon presumably costing about the same. And that's of course before you get into the question of whether 'good carbon' requires a fancy brand name. Or indeed whether 'good alu' is one that has a fancy brand name on it, or if a a generic (and cheaper) one is just as good.