I quote spiralsnipes blog here:

"“They have to make their money somehow, so of course they’re selling it” is being tossed around a lot. Those who are upset that they can’t “purchase” it with CE aren’t cool with that because CE was still paid for at some point; it represents someone else’ dollars which they’ve bought with their time invested in the game. Both sides are correct as far as facts are concerned.

There is one problem with all of that, which likely has something to do (but not everything because of the Steam side of things, which is a whole other issue for distribution for OOO, and upset for many players) with the decision to make it purchase only: Demographics.

The #1 demographic for new content for the game is the endgame player base who have been clamoring for new content for what sometimes seems since the start of time.

The problem here is that if this expansion were to cost as much as 3000 CE (roughly double what it actually costs) most endgame players would be able to afford this without denting their stockpiles of CE/crowns. This isn’t a problem, except for the bottom line “how much money does this addition make?” It kind of defeats the purpose of releasing a content pack for OOO, because it hasn’t generated any new income from those players, just the ones who had to buy CE ($$ or in game) to get it. (Obviously in the long term, that’s not the whole story - but that’s not business.)

Morals aside, it makes sense for OOO to have made it “purchase only” even if it makes players feel that they’ve been dealt with dishonestly, or divides the player base with “exclusive weapons.”
Hopefully the content or the weapons become more easily available later…"