Here we have a Nation net auction called Trademe. The used bikes there are always much better priced than new.
I've had well over 30 road bikes and only ever bought 1 new/complete (in 1995).
Yes technology does change fast with road bikes but mainly at the very high end (Di2 electronic shifting, carbon aero wheels etc)
That is fine if you've got a bottomless bank account, you want the latest and greatest to try and impress people or you are a Euro pro and seconds in races count.
I'm not a carbon fiber fan. See the bustedcarbon website.
You crash, it breaks & you throw it away. This happens to $6 k frames as it does for lower cost handlebars etc.
Carbon forks are a good idea (I guess).
I'm an aluminium fan. Many aluminium parts are just as light as carbon and cost less/last longer.
I hope this helps. Paul
Ended up buying a new Kona Jake The Snake.. Its a Cycle cross bike. I am loving it so far.
105 and ultegra
I am now preparing my own bike for the upcoming season (although the Spring is later as never before around here), so I will be subscribing to your channel, that watermellon helmet got me fully convinced!
Youtube will have vids on gears. It'll depend if you have grip shift of thumb shifters.
If you're just going to use it on the road it would pay to get some road tyres fitted.
Another thing to do is get it fitted for you - seat height, handlebar height and the gap between the seat and the bars.
There are bike fits on the internet. Sure, they may not be perfect for you but they're pretty good.