Caporegime
That is not too bad.
Most bikes will require you to change the saddle unless you are lucky with your arse shape. Derailleurs shouldn't really need to be changed though can wear out. Chain, chainrings and rear cassette are consumables and will wear out, as are wheels.
How long was you riding it that they needed to be changed?
Actually, the front derailleur may be the stock one, now that I think about it.
At stock the TDF has an aluminium fork and a full double chainset rather than a compact, so the previous owner replaced those fairly early on. I bought it off him about two years into his owning it, so he'd done the more expensive jobs, and I've now had it another two years and have done a whole lot more to it. I nuked the rear mech fairly early on when it managed to snag in the rear wheel, so had to replace that, the cassette wore out and got replaced along with the chain, I replaced the wheels about 18 months ago, and I replaced the saddle and shifters a couple of weeks ago. It's barely the same bike!!