As a compulsive petrol head, I have over the last 20 years built up a sizable collection of cars and motorcycles. All of my favourites are modified. It seems the more I like them, the more I improve & enhance them and I must admit on some of the favourites I went well overboard when I wasn't married with a family, had lots of time and such machines were more affordable back then.
My W124 300D Turb bought 6 years ago with the intention of no longer having to change family cars ever 3 years or so (& suffering depreciation), is very different to how it came from the factory, or how I bought it.
Employing used parts, hunted for over a period of years & bought cheaply when E500's were of low value and often broken for spares, it's morphed into what is essentially an original OM603 Turbo Diesel engined wide-bodied E500 inside & out.
Most of the parts are from the more powerful V8 model and as I'd expected, the car is all the better for the sum of the results.
A much more attractive looking, comfortable and capable car than when it was first built, retaining MB rock-solid integrity.
Next modification I'd like to do is a 722.6 gearbox (probably from a low mileage 2005 CL55), in order to satisfy my perversion for wanting paddle shift - since I can't have a manual transmission in a car that my wife drives predominantly, and silky smooth, fast gearchanges. After 6 years I'm running short of more things to keep improving it with.
Some will argue in terms of financial outlay to make it like this I'd make a loss if I ever sold it and they'd be absolutely right - but the reason I modified is precisely because I have no intention of ever selling it, so it's not a valid argument in this case...
My W124 is 26 years old now and still a rust-free car. My intention is to continue driving it for another 20+ years. Already it gets a lot of admiration as it drives our family of 4 around working dependently, daily. As another 20 or so years roll on, it'll be considered something increasingly interesting when seen on the roads, I daresay. Most of all, I like that it doesn't display any class of wealth. The unknown (to others) driver could be average, or wealthy - it doesn't suggest "I can afford a new car and you can't, everywhere it goes - as a top class Merc does). So at this age it's in a unique class, so to speak.
With the other vehicles I have (mostly Japanese sports models), the modifications I fitted, mostly a long time ago are similarly the best quality & design I could find at the time. Many of the parts used on them have since become discontinued & nowadays some of these most desirable bits fitted are worth considerably more than when they were available, which makes each car be more desirable as a whole than a completely standard and original one. Not least they're cars that appeal to driving enthusiasts that like purity of the experience and if enhanced & much improved regardless of cost, but concentrating on quality and refined under-stated taste, what's not to like?
I can't pretend to mean modifying cars was a good financial investment.
I'd call buying Bitcoins when they were first available, or investing in other financial instruments or precious metals, or even property - better forms of financial investment in the longer term. Cars or other large properties need to be maintained, used, have renovation, etc. all of which would diminish returns on financial outlays by comparison.
So I guess when we modify cars, it's for our own sense of triumph & enjoyment, not for the benefit of others per se.
If we avoid modifying, in order to try to preserve value then our experience & enjoyment of such cars may be diminished. I know in my own experience I've enjoyed the journeys of modifying and experiencing the differences each change makes and learnt a lot along the way.
I know most wouldn't agree, because their eye would be on the value of a vehicle - but if you'd never want to sell your modified vehicles, these things don't matter really.
Not least, when we sell our prized vehicles for which we had a particularly soft spot, the result is usually one of two outcomes:
Regret, or ultimately if we can still afford it, the whole process begins all over again - which usually leads to costs ending up higher than if we hadn't sold in the first place.
Maybe it's best to keep such things and just keep smiling as they continue to grow within our hearts and in desirability as they age and become rarer on the roads. So enjoy!
Just my tuppence worth...