Copyright of derivative works is additive: If you want to use an interesting photo of a sculpture, you need permission from both the photographer and from the sculptor.
In this case, Getty represents the photographer, but you still need permission from the sculptor.
Getty's license claims "Who owns the content? All of the licensed content is owned by either Getty Images or its content suppliers."
That line is wrong, of course, but every license comes with a limitation of liability so you can't sue them for being wrong: "Limitation of Liability. GETTY IMAGES WILL NOT BE LIABLE TO YOU OR ANY OTHER PERSON OR ENTITY FOR ANY LOST PROFITS, PUNITIVE, SPECIAL, INDIRECT, CONSEQUENTIAL, INCIDENTAL OR OTHER SIMILAR DAMAGES, COSTS OR LOSSES ARISING OUT OF THIS AGREEMENT, EVEN IF GETTY IMAGES HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, COSTS OR LOSSES. SOME JURISDICTIONS DO NOT PERMIT THE EXCLUSION OR LIMITATION OF IMPLIED WARRANTIES OR LIABILITY."
The right to use that image. Not the right to create derivative from it. Also licensing depends on end-use and can vary depending on the degree of use — a small print run of 500 copies of an ad using an image often has a different license cost than using that same image for a national ad campaign.
Terms of licensing are super clear when you buy stock work. What makes no sense is why the post office would even bother — there are plenty of public domain photos of the statue. Or they could have just had a mailman go shoot one and pay him $1000.
This is just incompetence, there wasn’t any ambiguity to what they were doing. They admit they used an image for commercial gain without knowing they were infringing — that’s negligence. They used that image because they knew it would sell more stamps. Even a basic legal review would have caught this — this sort of clearance/rights due dilligence is standard stuff. This wasn’t editorial and thus “fair use” would’t apply — this was used specifically to sell stamps. They can’t argue parody, satire or any of the numerous cases that might constitute fair use.
The post office made $70 million in pure profit from their misappropriation, the original art that led to that profit ought to be compensated accordingly. Had even a baby lawyer been consulted, they could have avoided this mess. Being a government agency doesn’t exempt you from the law.