Before I get into the math, I'd advise against causing the item to fill 2 item slots, it will turn into an annoying restriction that will significantly reduce its value and desirability. If it is taking up both slots, you might as well just give him both items and say they only work when worn together (and the helm affects rhinos instead of elephants).
Breakdown of the helm as best I can tell
-Gore ??
-permanent Endure Elements(cold) (1*1*2k)/2[24hr duration] == 1k
the following work with "elephants" only
-+5 competence HA 5^2 *100 == 2.5k
-+5 competence Ride 5^2 *100 == 2.5k
-+5 competence WE 5^2 *100 == 2.5k
-use activated Detect Animals/Plants (1*1*2k)*1.5[10min/level] == 3k
-use activated Speak w/ Animals (1*1*2k)*2[1min/level] == 4k
Now, those 5 are pretty heavily restricted, but I'm unsure exactly what percentage, if any, has been knocked off.
Further, it appears to me, that those 5 have also been considered "similar abilities".
Multiple Similar Abilities wrote:
For items with multiple similar abilities that don't take up space on a character's body, use the following formula: Calculate the price of the single most costly ability, then add 75% of the value of the next most costly ability, plus 1/2 the value of any other abilities.
The current total using "similar abilities"
4k + 0.75*(3k) + 0.5*(2.5k *3) + 1.5*(1k)[EE is dissimilar] == 11.5k
I suppose "dissimilar" is debatable, and all abilities were similar, but that still leaves us w/ 10.5k before accounting for the gore.
Either way, we're left guessing at the percentage reduction. I'll assume it was 30% (since it's the largest in the book, and these are very restricted).
8500 / 0.7 ~= 12150
If EE and Gore are dissimilar
12150 - 11500 = 650; 650 is 50% more for being different, /1.5 ~= 430
If EE is dissimilar, but Gore is similar
12150 - 11500 = 650; 650 has been halved for being similar, *2 == 1300
If EE is similar, but Gore is dissimilar
12150 - 10500 = 1650; 1650 is 50% more for being different, /1.5 ~= 1100
If all abilities were considered similar
12150 - 10500 = 1650; 1650 has been halved for being similar, *2 == 3300
Now, as BBT said, we can't actually know the exact calculation w/o the author stepping forward (very unlikely), but I do think you can use the formulae in the book to guesstimate what has been done.
I have no idea how far off I am w/ these, but a permanent Beast Shape I item would cost 60k according the formula. You're only getting 1 weapon and no other benefit. 430 seems a little low, but any of the others all seem pretty feasible, I'd probably go with ~3.3k and also call it similar for the Rhino Hide.
(The Charge portion costs exactly 1k, if you count the gore as similar, 3.3k +0.75*(1k) ~= 4k (==4050). I'd add 4k to the 9k for +3 armor, for 13,165. I realize this is ignoring that both are dissimilar to armor enhancement bonuses, but it seems to me like Rhino Hide already does that.)
If I'm mistaken about the similar abilities, it means a much greater arbitrary reduction was applied to this item, which throws a major wrench in approximating anything useful.
