A "viable billion dollar mission" includes all sorts of other things that are of value, including developing capabilities to do things that are strategically important, which I would claim is where a large majority of that billion dollars comes from. Similarly, I would expect that JPL would very much inflate the value of their own work. Everyone does.
Also, I see "incapable of being measured" with "broadly : indefinitely extensive" tacked on in the MW definition. There is no requirement there that "immeasurable" mean "large", just "incapable of being measured" with the expectation that it is used when describing things that are extreme. My most recent use of "immeasurable" was "immeasurably small" which I'm sure you would agree is a proper use.
Hosting the photos costs money too, which I don't think GP is considering.
If that's not your claim then I don't understand your valuation and the rest of the comment doesn't track.
And not to engage at a base level but my use of immeasurable is correct in being interpreted as "large" unambiguously, at least by Merriam webster.