the butler vintage is a great p bass no matter what the name attached to it is.
Its a bit subjective as to whether a 'name' instrument will sell more than a bog standard one. However it does seem to draw people to them perhaps in the first instance - along the lines of "oh! a *insert name here * bass I wonder how that is.
Presumably the hope from there is that the instrument is good enough to sell.
I have sig instruments from different manufacturers (not my sig! LOL) and I bought them because they did what I wanted them to do and not based on the associated name