Are you sure it was Namecheap that was selling that domain for a higher price or someone else listing it and trying to sell it. I'd expect most if not all short and pronounceable .coms to be taken. Some other registries (not registrars) do sell premium domains for a higher price themselves - i.e. ccTLDs are entirely up to the corresponding country and the new gTLDs also don't have as many restrictions on what the owner can do with them (e.g. they don't have to sell you domains at all).

If you actually have a trademark to the domain name then you can try the ICANN dispute process. If your entire claim is that you thought of the domain name but someone else bought it the good luck.