Yeah..
The creators & publishers want to market their property.
Imagine that..
( not to mention upc's are required by Diamond )
Yeah, hmmm... Who wants to market what? Collectors are going to know it is a phantom cover whether you slap an obnoxious logo on it or not. UPC I could deal with. UPC, Title, Phantom Logo Artwork, "Special #1 Collector's Item", profile pic of Larry, etc... no thanks. But I'm not the one dropping the cash to print it, so you keep on keeping on. I'll keep my cash in my wallet though.
Here's something you could easily do though, how about making some high quality poster prints of the covers (just the artwork) and have the artists sign a limited run. Sell em $20 a pop?