> 
> Yup, but the investment into developing suitable land for 
> leasing is quite high. You don't just "invent" new leases. 
> Its a poor example here as the overhead of creating new 
> domain names is much, much lower than developing property and 
> services to lease.

Depends on the property.  Many pastoral leases - are basically on
un-improved land.  It is up to the farmer to install fences, drinking
troughs, dams etc.

Also a registrant can invest a considerable amount in building brand
awareness of a particular domain name, which substantially adds to its
market value.

So you can sell unimproved domains (e.g those that have never been
delegated), or sell domains that have been used for a substantial period
of time and have considerable awareness in the community.

> 
> There are also restrictions on what you can and can't do with 
> your property - for example, zoning restrictions. You can't 
> pick up some residential land and then lease it out to industry.
> 

This is a fairly close analogy actually.

The rules for .com.au (commercial) are different from .id.au (for
individuals)
You can't transfer these between registrants unless the registrants meet
the relevant criteria.

The .com.au licence is a right to use for a particular purpose.

Regards,
Bruce