i'm not getting the connection you're tying to make regarding 'upgrading' to a 4-core from an 8-core.. (although if you did that between a 2009 mp and a 2013 mp, it would in fact still be a performance upgrade.. albeit slight in certain areas)
but why aren't you comparing a 2009 8-core to a 2013 8-core.. the performance enhancement between the newer and older becomes much more apparent.. it could definitely be considered an upgrade then.
at least you realize that's nothing but a wild guess
Because some people know that they cannot win their argument on a direct comparison so they have to resort to flim flam. Trouble with comparing prices from 4 years ago do not include inflation, cost of implementing new technology vs old. More performance cost more money.