I think there is an issue with changing standards too, whilst you may still love riding the bike you have, they are just bikes at the end of the day, if you had bought a £6000.00 26″ wheeled bike 3 years ago, it is now a lot less desirable purely because of fashions in the industry. It is a lot of money to invest for something that may depreciate so fast, that is fine if it truly is going to be used for the next 10 years, but i tend to find that those that pay top-end for bikes, are often also the ones that follow fashions most closely.
I tend to like to have a mix of bikes instead of one really expensive one, i’ve a Salsa Beargrease fat bike which is built all with Hope parts and the like, but all second hand and is ace for the great beaches near me, that then has 29+ wheels for something different, i’ve a Stooge 29er SS, a Salsa Fargo for bikepacking trips, a SS CX bike for winter road riding and escaping down bridleways when mood takes me and a road bike, so every base covered and all were built using second hand frames and most parts except for the grinduro CX bike.
It means i can ride a different bike depending on mood, where i want to ride and who i am riding with, i find that more fun than one “super- bike” where i will cry a little inside each time the paint scratched!