You don't really need that item. Yes, it's an item from the Boutique/Item Shop, but it will just give a bonus to the inspiration you gain.
I suppose the question that we should be asking is "If I don't buy the item, will my earned inspiration be less than now?"
If the item gives a bonus above and beyond the current level, but not using it has no effect **compared*to*now**, then it is just a way of getting a reduction in time.
If, on the other hand, the rate of inspiration gain is reduced *compared*to*now*, and the item makes up the difference, that is P2W (AOP: pay in cash-money or pay in gold-grinding-time, up to you to choose) of the worst sort. (The second-worst sort is the one where the rate is reduced and the item *more*than* makes up the difference.) It's the worst sort because it would say that they took something that worked about *that* well (not great, but not disastrously bad either), damaged it, and said, "here, pay us some money to undo the damage," in a notionally f2p game.
So: which is it? If a player does not buy the item, is his inspiration gain reduced compared to 5.*? If he does buy it, is it higher than in 5.*?