Originally Posted by GlennR

I have a 2016 that can take a 38mm but it's a CX bike. My road bike can fit 25mm, 28mm will not fit... and i'm OK with that.

The biggest thing is the frame. a $9000 2015 bike frame will still be better than a $2500 2020 frame. Dura Ace Di2 from 2015 is better than 2020 105. 25mm tires on carbon rims is better than 30mm on cheaper alloy.

Both bikes will be 11 speed, thru axles, disc brakes and 28mm+ tires just don't make as big an improvement over a bottom level carbon compared to top level.

It all depends on the condition. Replacing the bottom bracket, cassette, chainrings, chain, tires and brake pads can easily add another $1000.