I'm not an expert on his signature. However, James is exceptionally tough to land in person. He has an exclusive contract with Upper Deck. He only signs for them. So the vast majority of authentic balls on the market are UD items. With the price to match.
It's not impossible to corner Labron, but if somebody was going to hang out at a hotel lobby or track him down at a night club or restaurant, they would not have him sign a cheap $40 indoor/outdoor ball from Walmart.
Odds are overwhelming that this ball is not authentic. PSA is relatively good with modern athletes. They are by no means the be all and end all of authenticity, but I would bet money this is a forgery.
An authentic Labron James ball sells for around $1,000 to $1,250. There really are no deals. I would fight for a refund.