TLDR: You are in control of the value.

Self-Assigned Value

I would start by just regarding the skin and the Funko Pop as objects. This would theoretically also apply to any additional digital content in non-online software.
There is a high probability that you value such objects. This does not have to be quantitatively expressible, but there are connections you form. These could be based on aesthetics, admiration from others, or the object embodying a journey you went through.
The point is, you decide, or at least have the potential to determine, how important those objects are to you
This should not be confused with the metric “market value.” Obviously, you can base your own evaluation of an object solely on that, but they still are to be regarded as mostly independent. This is easily shown by the concept of price per value. If there were no value that is decoupled from the price, such evaluations would be absolutely meaningless, as all comparisons would evaluate to 1. This is also why these comparisons cannot directly be described as numbers, such as price/computation, but are an accumulation of specific metrics you ranked based on their importance to your individual specific use case.
Person A values efficiency more highly than pure computation, so even the computer with a higher price/computation/power usage might be worse value than the one that just exceeds in power efficiency. This changes for Person B, who is not interested in power usage and just wants raw performance.\

Control

In this section, the two objects diverge from each other in terms of who controls what. You could store your Funko Pop in a random cardboard box underneath your bed. This could be seen as an equivalent to removing any desktop entry of the game, or even deleting it, but you stood in control of these changes. You decided that the value of the object is not worth the clutter.
The difference is that with a Funko Pop, you will nearly always be in control of its value and accessibility. You put it on display on your shelf, or you throw it away. This is not so much the case with your Fortnite skin. Depending on the game, you might lose it, sell it, or even delete your account, but the skin is in every circumstance on a server, not under your control. If Epic Games decides to kill Fortnite or ban your account, this skin disappears. It would require trust in a foreign, for-profit company to safeguard your valuables.
I wouldn’t argue into the abyss that this is impossible, but it is definitely harder.