I din't nmind them planeshifting around to different places, and I at least one of the players is really hyped up about this ability.
Creating I figured Knowledge (the Planes) DC 15-25 (varies according to Plane) and Craft Wonderous Item feat,
I was figuring something like 1,000 gp each for the elemental planes (500 gp to create + 40 xp + skill check, and yes, they can take ten). Each fork must also contain a piece of the plane in question.
The +/- Energy Planes would be something similar. These planes aren't really popular with travellers. Perhaps up to twice the price due to lack of travellers who have been there. There is the issue of actually just popping away for a few minutes to the + energy plane to heal, but i guess this use two 5th level spell slots isn't much of an issue.
The real problem is the transitive planes; the Ethereal Plane, the Shadow Plane and the Astral Plane; as all these planes grant further access to other planes and realms of existance. On the other hand, they are readily available albiet with higher level spells, and the number of travellers who have visited these planes is numerous.
Given that Etherealness (in 3.0) is a 6th level Cleric spell, and that you need to find your way back, as well as actually being physically present on the Ethereal, as opposed to actually being ethereal, I was assuming a price around 2,000 gp to 5,000 gp. I would like to get a more precise figure. Also to consider is that these spells increased in level in 3.5 e, and that the armour of etherealness is +5 equivalent (costing at least 36,000 gp in 3.0 and exactly +49,000 gp in 3.5)
The Shadow Plane is available at 7th Wizard level and so should be even more expensive, but it has fewer uses (mostly just rapid movement, but as plane shift randomly relocates within 5 miles anyway, it seems almost pointless unless there is another reason for going there.
What about the Astral Plane? Once access is granted to this plane, nearly all planes become accessible. Astral Projection is a 9th level spell, and while also grants other powers, also comes with great risks. I was considering 9,000 gp
And the Outer Planes? I grant all clerics with the spell a tuning fork attuned to their god's home plane, but how much would a fork attuned to one of the hells cost?
Looking forward to some more feedback/thoughts/experiences on this topic