Sorry to say that you are way too last for the top 100 last names for the western world. They are all taken for .eth :(
Last names can be really interesting because you are more likely to get a buyer for last names that first names.
- Will.eth can only be bought by people name will
- Smith can be bought by all the smith in the word which is a larger number of people
And with .eth domains, your can even do a sub domain making us possible to do
So I would say last names are at least 10 times more valuable then first names.