Yes, impatience. Some buy CE because they love the game and thus want to reward OOO, some buy CE for the bonus items, but most purchases were because of impatience.

Usually MMOs will have various measures in place to encourage you to spend money. For example, in Puzzle Pirates (another F2P by OOO) your items decay over time, requiring you to work hard to earn enough in-game currency so you can buy doubloons (equivalent to Crystal Energy), or buy doubloons with real money, in order to replace your items. Other MMOs might have restricted areas or powerful items available only to paying customers.

But Spiral Knights is a free-to-play MMO that don't actively pressures you into paying. Everything is based off Crystal Energy, which you can buy with Crowns, which you can get by using a regenerating resource, Mist Energy.

Which means, you can access all contents of the game without ever needing to pay, if you make use of your Mist wisely, creating Crowns to get Crystal.

It takes less than 100 Energy to complete a single tier, if you don't need any to revive. The average profit in crowns is about 6K, the actual amount varying according to maps generated.

Which means, you can almost break even, gaining back enough Crowns for Energy used. Before the recent CE price inflation you can often make a profit.

People said the CE price is too high, they are unable to break even, and that is a problem.

My question is: Why is that a problem? Who said it is your right to be able to break even? Why should the game let you get into a positive feedback loop and play forever (or until you need to rest)?

I'd say not being able to break even is the whole point. OOO can't and shouldn't be paying for non-stop server usage and get nothing in return.

This is the contract of Spiral Knight's free-to-play model - you get 100 Mist to play with, make the most out of it. If you want more, you can be patient and work for it via in-game currencies, or you can pay for Crystal so you can what you want right now.

I started playing around the time Snarbolax was added, and have never bought any Crystal. I don't have accurate statistics, but I'd say the average price of CE was about 6K, with the lowest about 5K (shortly after Blast Network) and highest about 7K (Power Surges). I didn't buy extra Crystals during Power Surges other than playing the game in double dose. When I reached The Core on the same day I gained T3 clearance, I checked the login screen and it said my total game time was 4 days 20 hours. I play about 1.5 - 2 hours per day (yes, I mostly solo and play slowly), double the amount on weekends while using a little Crystal for elevators. That's not really that long, considering I made many mistakes (low-tier-dead-end items, time spent chilling around and chatting, recipes learned but never used, etc.), and I haven't used AH to make Crowns at all.

tl;dr Version:
1. OOO cannot and should not allow players to play for free forever. So making sure players can break even on Crowns vs. Energy spent is not something OOO needs to do.

2. If you feel you must get those CE right now, it's Spiral Knight's F2P model talking to you. Purchase Crystal, or be patient.

3. A Crystal price less than 7K is still pretty reasonable, considering the time I needed to craft a full set of 4* items and reach The Core.