“It’s not terrible news, but it’s not good news, either,” a NASA official said of a new issue found recently during testing of the James Webb Space Telescope. https://t.co/pcIvLTTfgT

— Jeff Foust (@jeff_foust) May 3, 2018

The JWST has a history of major cost overruns and delays which have resulted from outside factors such as delays in deciding on a launch vehicle and adding extra funding for contingencies. By 2006, $1 billion had been spent on developing JWST, with the budget at about $4.5 billion at that time. A 2006 article in the journal Nature noted a study in 1984 by the Space Science Board, which estimated that a next generation infrared observatory would cost $4 billion (about $7 billion in 2006 dollars).[49] Because the runaway budget diverted funding from other research, the science journal Nature described the James Webb as "the telescope that ate astronomy" in 2010.[88] In June 2011, it was reported that the Webb telescope would cost at least four times more than originally proposed, and launch at least seven years late. Initial budget estimates were that the observatory would cost $1.6 billion and launch in 2011.[89]

The telescope was originally estimated to cost $1.6bn but the cost estimate grew throughout the early development reaching about $5bn by the time the mission was formally confirmed for construction start in 2008. In summer 2010, the mission passed its Critical Design Review with excellent grades on all technical matters, but schedule and cost slips at that time prompted Maryland US Senator Barbara Mikulski to call for an independent review of the project. The Independent Comprehensive Review Panel (ICRP) chaired by J. Casani (JPL) found that the earliest possible launch date was in late 2015 at an extra cost of $1.5bn (for a total of $6.5bn). They also pointed out that this would have required extra funding in FY2011 and FY2012 and that any later launch date would lead to a higher total cost.[90]

On 6 July 2011, the United States House of Representatives' appropriations committee on Commerce, Justice, and Science moved to cancel the James Webb project by proposing an FY2012 budget that removed $1.9bn from NASA's overall budget, of which roughly one quarter was for JWST.[91][92][93][94] $3 billion had been spent and 75% of its hardware was in production.[95] This budget proposal was approved by subcommittee vote the following day. The committee charged that the project was "billions of dollars over budget and plagued by poor management".[91] However, in November 2011, Congress reversed plans to cancel the JWST and instead capped additional funding to complete the project at $8 billion.[96] Termination of the JWST project as proposed by the House appropriation committee also would have imperiled funding to other missions, such as the Wide-Field Infrared Survey Telescope.[97]

The American Astronomical Society issued a statement in support of JWST in 2011,[98] as did Maryland US Senator Barbara Mikulski.[99] A number of editorials supporting JWST appeared in the international press during 2011 as well.[91][100][101]

Some scientists have expressed concerns about growing costs and schedule delays for the Webb telescope, which competes for scant astronomy budgets and thus threatens funding for other space science programs.[102][85] A review of NASA budget records and status reports noted that the JWST is plagued by many of the same problems that have affected other major NASA projects. Repairs and additional testing included underestimates of the telescope's cost that failed to budget for expected technical glitches, missed budget projections, and evaluation of components to estimate extreme launch conditions, thus extending the schedule and increasing costs further.[85][89][103]

One of the reasons why the cost grew so much is that it is difficult to forecast the cost of development, and in general budget predictability improved when initial development milestones were achieved.[85] By the mid-2010s, the U.S. contribution was still expected to cost $8.8 billion.[85] With the U.S. and international funding combined, the overall cost not including extended operations is projected to be over $10 billion when completed.[104] On 27 March 2018, NASA officials announced that JWST's launch would be pushed back to May 2020 or later, and admitted that the project's costs might exceed the $8.8 billion price tag.[87] In the March 27 press release announcing the latest delay, NASA said that it will release a revised cost estimate after a new launch window is determined in cooperation with the ESA.[3] If this cost estimate exceeds the $8 billion cap Congress put in place in 2011, as is considered likely, NASA will have to have the mission re-authorized by the legislature.[105][106]