Users of collapsed bitcoin exchange Mt. Gox have been trying to get their money back for a decade. From the beginning of July, the company will begin paying users back their funds.Kiyoshi Ota | Bloomberg | Getty ImagesMt. Gox, the Japanese bitcoin exchange that collapsed into bankruptcy a decade ago after a major hack, is finally set to repay creditors, who are being rewarded handsomely for their patience.Up to 950,000 bitcoin were lost in the 2011 hack, at a time when the cryptocurrency was trading for a tiny fraction of its current value. Some 140,000 of those coins were recovered, a haul that, at today’s prices, means that roughly $9 billion worth of bitcoin will be returned to its owners.Among the claimants is Illinois native Gregory Greene. Soon after the exchange declared bankruptcy in February 2014, Greene filed a class action lawsuit against Mt. Gox and its former CEO. Greene said at the time that his frozen account contained $25,000 in bitcoin, though he didn’t disclose the exact number of coins in his wallet.Bitcoin was then trading at roughly $600. Today it’s worth over $60,000. That suggests Greene’s lost stash, at current prices, would be worth about $2.5 million, a 10,000% gain. However, it’s unclear how much he’ll receive in the payouts, which are expected to start rolling out in July.John Glover, chief investment officer of crypto lending firm Ledn, said creditors are about to get a historic windfall.”Many will clearly cash out and enjoy the fact that having their assets stuck in the Mt. Gox bankruptcy was the best investment they ever made,” Glover told CNBC.What was Mt. Gox?Mt. Gox was an online marketplace where people could buy or sell bitcoin using different currencies. At the height of its success, the platform was the largest spot bitcoin exchange in the world, claiming to handle around 80% of all global dollar trades for bitcoin.The company, whose acronym was created from the name “Magic: The Gathering Online Exchange,” shuttered in February 2014 after a series of heists.Mt. Gox blamed the bitcoin disappearance on a bug in the cryptocurrency’s framework. While users were receiving incomplete transaction messages when accessing the exchange, in reality coins may have been illicitly moved by hackers out of their accounts, Mt. Gox said.On Monday, the court-appointed trustee overseeing the exchange’s bankruptcy proceedings said distributions to the firm’s roughly 20,000 creditors would begin next month. Disbursements will be in a mix of bitcoin and bitcoin cash, an early offshoot of the original cryptocurrency.Alex Thorn, head of research at crypto asset management firm Galaxy Digital, said in a note last month that the vast majority of creditors he’s spoken with have said they will take a payout in-kind, meaning in cryptocurrency rather than fiat. They’ll also be largely holding on to the assets.Many of the top holders with claims to Mt. Gox assets, he said, are well known in the bitcoin world. They include early bitcoin investor Roger Ver, Blockstream co-founders Adam Back and Greg Maxwell, and Bruce Fenton, former executive director of the Bitcoin Foundation.Some will ‘take the money and run’Based on conversations with institutional investors due for payouts, “we do not believe there will be significant selling from this cohort,” Thorn wrote.However, Glover, who was previously a managing director at Barclays, said there’s still likely to be significant selling among creditors who, after years of waiting, have the opportunity to lock in massive gains.”Some will clearly choose to take the money and run,” said Glover.Analysts at JPMorgan Chase said the potential for heavy selling from Mt. Gox creditors creates “downside risk” next month, though it would be short-lived.”Assuming most of the liquidations by Mt. Gox creditors take place in July, [this] creates a trajectory where crypto prices come under further pressure in July, but start rebounding from August onwards,” the analysts wrote.There’s also the likelihood that a number of bitcoin investors in Mt. Gox have already cashed out. In the 10 years since the exchange filed for bankruptcy, a secondary market sprung up for those who wanted to liquidate their bankruptcy claim. Those who have held out are the true believers, Thorn said.”Thousands of these creditors have waited 10 years for payouts and resisted compelling and aggressive claims’ offers during that time, suggesting they want their coins back,” said Thorn. He said he expects limited selling pressure but acknowledged that if even 10% of the bitcoin distributed is sold “it will have a market impact.”Certain tax consequences may deter sales.Luke Nolan, ethereum research associate at digital asset management firm CoinShares, said a big reason Mt. Gox creditors opted for in-kind reimbursement has to do with the tax implications. And JPMorgan said in a note on Monday that people are leaning toward accepting their disbursement in crypto, “either for tax reasons or because they think that liquidating now would void potential further price gains in future.”Glover said there are ways to sidestep a big capital gains tax while still taking advantage of bitcoin’s huge run-up in value.”Those in jurisdictions with capital gains tax may elect to hold their positions to avoid this huge tax bill,” Glover said, “and instead use their bitcoin as collateral to borrow dollars, thus monetizing the bitcoin without having to sell it.”Don’t miss these insights from CNBC PRO