The site you saw is run by Public-Root, one of the many alternative root zone operators. These are essentially rogue organizations that create/sell custom TLDs that aren't sanctioned or recognized by ICANN and only exist on their own private root DNS servers.
So, technically, they're right, you can buy a custom TLD from them for $1000. The only problem is that no one, not even you, will be able to resolve the TLD or any domains under that TLD because pretty much no ISPs use these alternative root DNS zones. Nearly all ISPs stick to ICANN's official DNS root.
Another problem with alternative root zones is that it allows different root zone operators to sell the same FQDN to different people, resolving to different servers. This happened when Pacific Root created
.biz before ICANN sanctioned the creation of the
.biz TLD. Later, when ICANN officially sanctioned
.biz and delegated it to Neulevel's root servers, there became a conflict due to overlapping DNS records for
.biz domains sold by Pacific Root and those sold by Neulevel. In effect, some people would type in
foo.biz and it would resolve to one IP address as given by Pacific Root, while someone with a different ISP would get pointed to another IP as specified in Neulevel's official root servers.
Of course, this was gradually resolved as alternative root zones have pretty much been discounted (as evidenced by the horribly dated and poorly maintained self-promotional websites linked to Public-Root) since the use of alternative root zone would inevitably fracture and destabilize the internet. But this hasn't stopped these unethical companies from setting up semi-official-sounding organizations to link to using fake trustmarks (using early-90s-era graphics) and trying to scam unweary visitors out of their money.