To preface, at the time of writing this post, Celestial Orbitguns are selling for upwards of 220-240ke.
I don't have to explain to you that this is an extremely inflated price, especially considering that only a year ago as of writing this post, Orbitguns were selling for 120ke clean.

So what happened?
Part of the increase in price is due to Grey Havens halving of the rate of getting Orbitgun (or any specific celestial equipment from equinox) that occurred in late 2019.

Prior to this, Equinox boxes would have any two of the four celestial items on a rotation, one item would be shifted out every 6 months (when the promo would return,) and another would replace it.

For example:

• Fall Equinox 2017 contained Celestial Vortex & Celestial Shield
• Spring Equinox 2018 contained Celestial Shield & Celestial Orbitgun (replacing Vortex)
• Fall Equinox 2018 contained Celestial Orbitgun & Celestial Saber (replacing Shield)
• Spring 2019 contained Celestial Saber & Celestial Vortex (replacing Orbitgun)

As of Fall 2019, there is no rotation, and all of the equipment are available from any given Equinox Prizebox purchased during/after September 2019.
However, as a trade off, the 1% chance to get an item from the equipment pool was not increased to compensate, so effectively the chance of pulling an Orbitgun has halved

Ideally, Orbitguns value should be 150ke, considering that, while they're harder to pull, there will always be new Orbitguns in the market every 6 months, however due to some players deciding to artificially inflate Orbitgun prices by buying at market price and then later selling for much greater, Orbitguns are currently 200-230ke. Some players are desperate to own an Orbitgun, and are buying into these inflated prices, incentivising players that are inflating the value to continue doing so, creating a cycle of inflation.

So what can you do as a buyer?

Its simple, but not necessarily easy. All buyers should try to aim not to overpay for Orbitguns. Buyers have power over the economy too, and if they decide they do not want to pay for an item at a high price, sellers that are holding onto those items will have to wait, or sell for a price that buyers are willing to pay. This could be seen as "voting with your wallet".
On top of that, spreading this node around to anyone you see trying to purchase an Orbitgun helps, as it'll make them think twice before offering more than they should.

TL;DR

People are actively trying to increase the price of Orbitgun by buying at market price, and then reselling for many thousands more
As a buyer you counter them by refusing to pay their inflated prices
Help make the value of orbitguns reasonable again by spreading the word (and this node/123618).