Originally Posted by
johnny99
If you bought a dirt cheap used bike intending to spend the money to restore it, then go ahead and do it.
Big money upgrades to new bikes never make sense. Upgrading worn out or poorly fitting parts makes sense, but modern bikes are well balanced enough that upgrading just for fun is not cost effective.
In general I'd go along with this.
I bought a used bike for £350 and since then I've bought rack and panniers (£100), new saddle (£40), new bar tape with gel pads underneath (£20) and built a new wheel (£200). So there's more than the bike cost before considering chains, cassettes, tyres etc (roughly £150 on tyres, £40 on chains and £40 on cassettes).
I'd continue to spend at that kind of level although if I decided I wanted to move from Tiagra to Dura-Ace parts I think I'd just buy a new bike than upgrade to that extent.