Following is a guest post by Diplomat contributor and security analyst David Axe.

It has been more than a month since the Chengdu J-20, China's first stealth fighter prototype, made its debut in grainy Internet photos. The 70-foot-long J-20 flew for the first time earlier this month, and has now apparently embarked on what could be an at least 8-year test programme to prepare it for mass production.
All over the world, governments are reacting. The Pentagon urged calm, stressing the continuing long lead US aerospace has over any competitor. But Vice Adm. Jack Dorsett, head of US Navy intelligence, admitted Washington has at times ‘under-estimated’ the speed and effectiveness of Chinese military developments. Taiwan, in an apparent panic, arranged a public test of its air defences and reeled as decrepit missiles malfunctioned and plunged into the sea. Meanwhile, India heralded the operational debut of its first (non-stealthy) home-grown fighter and plowed ahead on developing a stealthy follow-on.

For all that, no one knows for sure how advanced the J-20 truly is, or what Beijing intends to use it for. Observers all over the world have pored over available photos and videos hoping to glean insights into the fighter's design. One Australian think tank even imagined a future Taiwan war scenario entirely built around a massive force of J-20s sweeping the skies clear of American warplanes.
But there's one key question no one has really asked. Indeed, it might be the single most important question of all—how much does the J-20 cost? No one knows for sure. Analyst Andrew Erickson has guessed $110 million per plane. That compares favourably with the cost of US stealth fighters. Not counting development, a single F-22 costs around $130 million. Again not counting development, the newer F-35 is itself around $100 million per copy.
Considering China's meteoric economic growth, the J-20's cost might seem irrelevant. If so, it would represent the first time in modern history that a fighter programme has managed to boost free of financial gravity.
Consider: the principles of fighter design are no secret. The United States, Russia, China, Britain, France, Germany, Sweden, Japan, South Korea and India, among others, all design and build meaningful numbers of high-performance aircraft. Countries as small as Serbia and Taiwan have produced their own fighter types in recent decades.
Even stealth technology is hardly a secret. ‘The fundamentals of stealth start with shaping,’ longtime aviation journalist Bill Sweetman explained. In that regard, ‘the Chinese could have learned all they wanted from a visit to a hobby shop,’ where companies such as Testors sell realistic scale models of existing stealth warplanes.
The real reason there are so many fighter manufacturers in the world, but so few stealth fighter manufacturers, is cost. To date, several countries have outlined possible stealth fighters (Britain, Germany, Japan, South Korea, India and even Turkey) but only three have produced flying prototypes (the United States, Russia and China). Of those three, only the United States has actually mass-produced stealth planes. The MiG-1.44 was too expensive for the cash-strapped Russian air force when that plane debuted in the late 1990s. Even today, with improved finances, Russia admitted it couldn’t build large numbers of its newer T-50 stealth fighter without Indian co-financing.
In the United States, cost is the major factor in how many stealth fighters the country builds—and how fast. Citing cost, in 2009 the Pentagon cut short the F-22 fighter programme at just 187 copies after spending more than $64 billion over 20 years. Now the Pentagon is committed to buying 2,400 F-35s at a total cost of nearly $400 billion over a period of decades. To ensure the F-35's cost doesn’t rise, US Defence secretary Robert Gates has repeatedly delayed mass production in favor of more careful testing.
If money is the biggest constraint for the US stealth fleet, it must surely be a factor for the Chinese air force, too. After all, the annual US military budget exceeds $600 billion. By any measure, the Chinese spend much, much less. ‘Production of 20 (J-20) aircraft per year beginning in the 2014 timeframe at $110 million per plane would still probably account for only about 2 percent of China’s defense budget,’ Erickson proposed, as though 2 percent were a small figure. Even the $10-billion-a-year F-35 programme—the costliest weapons scheme in the world—gobbles up just 1.5 percent of the Pentagon's top line, yet still represents a major financial risk.
In the end, it might not matter how fast, heavily-armed and stealthy the J-20 actually is. The new jet's most important attribute could be its cost. For its price tag is the thing most likely to prevent the J-20 from appearing in large numbers and, potentially as a result, altering the Pacific balance of power. 
Even if Beijing did decide it was worth spending a record sum on J-20s, that would surely result in some weakness elsewhere in the Chinese defense apparatus—a principle Gates pointed out while defending the F-22 cut. ‘Every defense dollar diverted to fund excess or unneeded capacity—whether for more F-22s or anything else—is a dollar that will be unavailable to take care of our people, win the wars we are in, to deter potential adversaries and to improve capabilities in areas where America is underinvested and potentially vulnerable,’ he said.
The same would surely apply to the Chinese.