It's $280 + 20 shipping right? That's every so slightly more expensive ($300) than Ebay currently ($299). Do they do free returns or something?
Do you ball? Different shoes give you a different feel, different results. You sometimes want speed and sacrifice cushion. You sometimes want "court feel" and sacrifice padding and cushion. Sometimes you want cushion but the result is a heavier shoe. And that's just your own game. Take for instance the (overhyped but still relevant) decision he made last night to start trying to guard Murray. Well now if you've gone full cushion and upped the weight on your shoes, you're not going to have the best footspeed you'll need to guard that dude. And in fact on that one play where Lebron put his hands behind his back and tried to move his feet - got called for a foul because he wasn't quick enough.
So he could switch to the lows for a lighter feel, but he's been mostly avoiding those since they're tight as hell. I'm sure you've seen the video of him putting them on and basically jamming his feet in there.
So there's considerations with every shoe, and you can wear test them all you want in a practice environment, we all know game speed is something different. And even all that isn't touching on places the shoe could hurt - pain points - after extended use, or how the upper might hold up or break down under the stress of playoff basketball. Remember in some of those shots Lebron had the tongue up, so even then he wasn't wearing the shoes standard.
So it all comes back to - is now the time, with 1 game to win to get to the finals, or then IN the finals, to game test new shoes? Nah, not really.