There is no $ amount as a price of admission.
For me it is about the rush I get when I hear something new or different in a record that sounds better. At times it may be from a minor change that has big impact or a relatively bigger change that may only has a small impact.
If you appreciate reproduced sound quality, seek to have it in your house and realize you can always get something better and can live with that you are a sane audiophile. If you are on the never ending hamster wheel of upgrades, my condolences. At this point, I am happy with my system's sound and realize the limitations of my room acoustics and only change equipment when something breaks or wears out.
I do seek out better sounding records of my favorite recordings however....luckily that is a fairly reasonable number.