I get the fun bit, the tinkering with bikes (I can also strip down and rebuild a traditional road bike, although my hydraulic braked bikes … they defeat me and go to the qualified bike mechanic). I also get the tinkering with a bass for fun. That said, the furthest I’ve gone is installing strap locks and custom pick guards.
But, I simply can’t see the point in spending loads on upgrades, if the basic construct of the object isn’t actually that good.
I had a Trek 1000, @JustTim. Actually, I’ve had two over the years - a silver one and then a black one. Even with swapped out parts, they weren’t a patch on the 5200 I also had, or the Madone, and certainly couldn’t compete with the Cervelo, when I bought that. Of course, the 5200, the Madone, the Cervelo, were far more expensive machines, but they all had something in common, and that was a quality, lightweight, carbon frame.
Same with basses, @ElGatoVermelho, yes you can mod a cheap bass, and of course, you can have fun doing so, but as @howard stated, at it heart, the bass will still be a cheap bass. I’m not trying pick a fight, it just that in my opinion, I would rather start with something better, that doesn’t really need modding because it’s good in the first place. The main reason I love second hand is that one can buy some seriously good stuff for a lot less than retail, if one is prepared to wait.
Of course, we all have different views… Vive la différence!