My understanding is that the Hornady dies for the .50 AE are NOT carbide.
If you check out the link that mbartel supplied, the Hornady die says "steel".
I seached all the die makers a few years ago. The lierature for the Lyman dies said "carbide", but I called 'em and the verified that they were NOT carbied.
It seems that the problem with the .50 AE is that to put in the carbide ring, there is not enough "meat" in the die. The only way to work with this problem is to go with a larger diameter die, hence the "RCBS Carbide 3-Die Set with Taper Crimp 50 Action Express (1 x 14 Thread) with 1-1/4 x 12 Thread Adapter Bushing" which around $345 at MidwayUSA.
It funny....there are carbide dies for the .500 S&W. I think I read that the carbide ring for the .500 S&W is not the same as for the .50 AE...so they were able to squeeze it in to the "regular" die. Don't ask me - it seems to me a .50 cal is a .50 cal. People have suggested, but told it can not work, to use the .500 S&W sizing die to size the .50 AE. I guess the taper is different or something.
$345 will buy you a lifetime's supply of sizing lube (unless you reload a lot)!