Officer, I'll find you as soon as I can.
I think it was @Lannister who did something really cool during a DM event, there was some kind of anti-magic field in certain areas of the quest, so potion didn't work (we had healer's kit though). It forced us to plan ahead, be cautious and actually work as a team instead of buff-buff-buff-rush.
I really liked that idea. You can switch that up and down to balance the event.
But during normal quests, I think consumables should be easy and free to use until we have enough players to be able to constantly quest with 3+.
My 2 cents.
I actually prefer a world where potions are rare and wands even more, like CoA v2 or v3, but craft wand/potion needs a lot more care because it can reduce PVE as well.
XP cost for scrolls should be applied and it shouldn't be small. It directly changes the result of a PVP battle, it can impact another player's good time for worse.
If there's a XP toll and suddenly potions or wands become luxury we might end up with people giving up on questing simply because they don't have an optimal party. So it doesn't really matter if quests can be soloed or not, people simply won't do it (or at least the majority won't).
So, at one side of the spectrum potions and wand make up for lack of players, but takes away the importance of party/class formation.