This is just silly. The seller is hoping for someone with more dollars than sense. Calling this a "vintage" computer is either stupid or an outright lie. There are plenty just like it still serving duty in production environments today.
The comment about the condition of the box being just as important to collectors is also true. These machines are available all day long for under $200 and you can get one in pristine condition for under $400. Who is going to pay an extra $2600 for this raggedy box just because it's still sealed with factory tape? It's a nice computer, but it's hard to imagine that it will ever be a "collector's item". The G4 Cube seems far more interesting in that respect.
I'll admit that I'm not very good at predicting the future, but I feel pretty confident that the mid-range G5 tower is not going to be the next TAM
(and even the TAM with a nicer box
is not selling for nearly the asking price here).
Even if you hold it for decades, it's hard to imagine recovering the cost. What are you going to do if you buy it? Are you going to cut through the $2600 tape? What if there is no computer inside? What if you pass it down to your grandchildren to sell and it is only then discovered that the seller devised an extremely clever way to dispose of (and profit from) his dirty cat litter?