TLDR: I'm starting a Plane-hopping 5e campaign tonight with Level 2 PCs. What is an appropriate cost for a lower-level more restricted Plane Shift?

Obviously, our wizard doesn't know Plane Shift yet, but the whole concept of the campaign involves lots of Planar Travel. My players, when polled, prefer not to have a ship and use a more "mystical-feeling" travel method instead. Because I unintentionally already started to use some fabric/thread-themed language describing the cosmology, I came up with the idea of a "Quilt of Reality" that can be obtained in separated squares.

(EDIT to clarify: They would start with 0 squares and obtain them 1 (or maybe 2) at a time through large quests/dungeons/etc)

Each square would be attuned to a specific Plane, but I'm struggling to set a balanced scalable cost for Plane Shifting using this instead of the normal 7th Level Spell. Some ideas I've considered:

1. Cost of a spell slot. A decent cost in lower levels but quickly becomes trivial with a Wizard, Cleric, and Paladin comprising the party.
2. Cost of HP. Again, not easily scalable.
3. Monetary cost: Around 200-250 GP to buy or have one made. Once our Wizard learns Plane Shift, this will be allowed as a substitute material component.
4. Monetary Material Component Cost: Similar to Teleportation Circle, ink infused with the gem dust of the corresponding Plane Portal color (Amethyst for the Abyss, for example). Probably about 100-150 GP material cost.
5. Single-use square: Each quilt square can only be used once. My only concern is that this could make things feel very linear.
6. Something else?

My goal is to allow them to travel a good amount - at least once every 5-6 sessions. They could find a way to Sigil to access the portals there, or go through the Astral Sea, but at lower levels that's still quite an ordeal. (EDIT: I don't want to rely on Sigil only because in my opinion the portals/doors don't have any cost associated to them, they are portals that are already there. But I might tweak my idea to have the border pieces of the quilt all connect to Sigil, making those pieces much more common than the individual squares).