Memory is now worth more than oil. Staying that way will depend on how much the notoriously volatile industry can make recent changes stick.

The world's three largest memory-chip makers -- Samsung Electronics, SK Hynix and Micron Technology -- now carry market capitalizations of more than $1 trillion each. That puts them about 22% above the combined market cap of the world's three most valuable oil companies, even with Saudi Aramco weighing in on its own at nearly $1.8 trillion.

Values have soared even further down the memory chain. Flash-memory maker Sandisk has seen its market cap nearly triple since March and is now worth nearly as much as PetroChina -- Asia's largest oil producer.

Gains like that make memory stocks seem ripe for a fall, especially given how highly cyclical the industry has been historically. But recent changes in business practices make projected earnings far more certain. And against those future earnings, even trillion-dollar memory companies still look cheap.

Like oil, memory chips are widely seen as a commodity prone to violent price swings. But artificial intelligence is now driving demand for memory chips far beyond what existing suppliers can produce, which is driving up prices to previously unseen levels. Memory makers in turn are using their newfound leverage to get customers to sign long-term agreements.

Enough of those deals will recast the industry's business model in a way that will tame price volatility. The early signs of that effort are good. Micron announced the signing of its first five-year supply agreement in its last earnings report in March, and the company said at an investment conference last week that it has made "meaningful progress" on similar deals with other customers.

In its own report last month, Sandisk said five customers had signed long-term agreements -- enough to cover more than a third of the company's production capacity for the next fiscal year.

SK Hynix hasn't detailed how many of its customers have signed long-term agreements. But it has clearly talked with those customers about their future needs, given the disclosure in its last earnings call that demand "far exceeds" the company's supply capacity for the next three years. "Memory today has become so critical that customers now see memory price and supply uncertainties as key business risks," SK Hynix Chief Financial Officer Kim Woo-hyun said on the call.

The spending power of artificial intelligence's largest investors means a significant percentage of future memory production will be covered by multiyear contracts with more stable pricing terms. UBS analyst Tim Arcuri estimates that such contracts will cover as much as 30% of shipments of total dynamic random-access memory, or DRAM, next year. He thinks hyperscalers -- huge tech companies such as Microsoft, Alphabet's Google and Amazon.com -- have already secured around two-thirds of global production for the type of DRAM used in servers.

"Said differently, hyperscalers appear increasingly willing to exchange pricing for multiyear supply visibility and greater predictability around future deployment economics," Arcuri wrote in a report earlier this week.

Long-term contracts make future earnings from memory companies far more predictable. And those earnings are substantial. Micron's adjusted per-share earnings in the February-ended quarter exploded to $12.20 from $1.56 in the year-ago period. Wall Street expects earnings per share to top $60 for the fiscal year ending in August -- and to come in around $106 for the next fiscal year, according to estimates from Visible Alpha.

So at its current market cap of just over $1 trillion, Micron trades at less than 10 times projected earnings for the next four quarters. That puts its multiple in the bottom 10% of the S&P 500, with Sandisk not far above at around 10.5 times forward earnings.

The Korean players are even cheaper, with Samsung and SK Hynix in the six- to seven-times range, per FactSet data. The 30 stocks on the PHLX Semiconductor Index average a forward earnings multiple of around 26 times.

Memory may be the new oil, but memory investors aren't getting gouged at the pump yet.