Well, language here complicates things. We often conflate "cost" with "value" even though those are (and ought be) different things.
All of my firearms are valuable to me, even the tiny .25acp Beretta. That does not mean they were costly. Some will command more, significantly more, to replace than I originally paid. That's the nature of things.
Most I ever spent on a single arm was for the LE6922, most I ever sold one for was my Python. The one that would be hardest to replace is my minty 1943 SC 03A3. Followed closely by my Mossberg M-44. My Saginaw Carbine would not be easy to replace, either.
But, each are equally valuable to me.