I do not have Oriental Adventures, but here is how I would price it:
A feat is basically worth about 10000 gp. Impro Init. is a feat that adds +4 to you initiative bonus. Assuming the cost for a bonus to Init. follows the standard formula of (bonus squared) x (some gp value), we have: 10000 / (4 * 4) = 625 gp.
The price of an initiative bonus would be: (bonus squared) x 625 gp
To simplify the calculation, and to reflect the fact that a competence/enhancement bonus is generally inferior to an unnamed bonus, I would probably DM fait the bonus down to: (bonus squared) x 500 gp. That is to say:
+ 4 competence bonus to Initiative: 8000 gp
+10 competence bonus to Initiative: 50000 gp
+15 competence bonus to Initiative: 112500 gp
+20 competence bonus to Initiative: 200000 gp
This is probably too cheap. I cannot see *any* 20th level character being unwilling to shell out a paltry 200000 gp in return for a whopping +20 bonus to intitative.
Perhaps we should add a x2 in there (Basically, 'pricing' Impro Init. at 16000 gp instead of 8000 gp, as it is one of the better feats to have). 16000 gp for a +4 bonus to initiative is still very, very good, and I would certainly be willing to spend 100000 gp to get a +10 init. bonus at 20th+ level (at high levels, whoever wins intitative, wins).
+ 4 competence bonus to Initiative: 16000 gp
+10 competence bonus to Initiative: 100000 gp
+14 competence bonus to Initiative: 196000 gp
That is how I would price a item that grants a competence bonus to intitative checks in my campaign. Of course, IMC there are no Iiajutsu Masters with insane Iiajutsu focus (or whatever it is called. I do not have the setting), so please take all of my calculations with a large grain of salt....
Ja ne, ^_-
Yanei Wu