However the Fat david above is clearly a commercial product, so either they have a license to make it or the copyright does not cover it.

This is the section of Fair Use that would apply here.

Producers or creators of parodies of a copyrighted work have been sued for infringement by the targets of their ridicule, even though such use may be protected as fair use. These fair use cases distinguish between parodies, which use a work in order to poke fun at or comment on the work itself and satire, or comment on something else. Courts have been more willing to grant fair use protections to parodies than to satires, but the ultimate outcome in either circumstance will turn on the application of the four fair use factors.

For example, when Tom Forsythe appropriated Barbie dolls for his photography project "Food Chain Barbie" (depicting several copies of the doll naked and disheveled and about to be baked in an oven, blended in a food mixer, and the like), Mattel lost its copyright infringement lawsuit against him because his work effectively parodies Barbie and the values she represents

I doubt that, again looking at Ebay, there are lots of postcard being sold of him, some looks like they were made with a very poor camera.

Legally the post card sold on Ebay would breach the copyright laws protecting the statue unless properly licensed. Would it be worth the time and money to pursue a complaint against a foreign printing company selling illegal post cards, probably not. Issues like this can quickly fall into the whack-a-mole issue that exist in a few other areas. It goes a bit like this, an item is illegally added for sale, the item is noticed by the copyright owner, legal preceding take place and legal notice is sent to the the individual that is selling the item, asking them to remove it from sale. After a month or two the item is finally removed. The next day it is re-added under a slightly different name or from a different account and so on. What ends up happening is the copyright owner needs to constantly pursue their rights, sending letters and monitoring the situation only to watch items almost instantly reappear. The individual who is knowingly breaching their copyright does a little dancing and a bit of up and down of adding or removing things, but continually has an incoming revenue stream. Pretty safe in the knowledge that it just won't be worth the time and cost for the copyright owner to actually pursue any real legal proceedings against them.

Another thing that is worth noting on copyright is it is often based on case precedent, not any hard and fast rules of what is or isn't protected. So in other words courts will decide on a case by case basis, based on previous rulings that set precedent. So basically a decision that could influence the rest of your life will likely be based on how well your legal representation can convince a judge that you own or have independently created an item and how well those suing you can present evidence that it infringes on their own legal rights. Cases can go on for years and cost well into the millions of dollars.