It all depends how badly you want the domain.
A large number of domain traders (or even squatters) buy domain names with the aim of selling them to 'END BUYERS'. In this market domain traders or squatters know that they will make good profits from selling to domain names to end buyers, who need these domains badly.
In valuating a domain name you need to look at a number of factors, which include the length of the domain, brandability of the domain, current type-in traffic or normal traffic to the domain, is the domain generating traffic, etc. All these factors increase the value of the domain.
With your example, ABC.co.za will be quite expensive, as it is a 3-letter domain, ABC (referring to the alphabet) is definately a premium domain which will have some traffic from people just typing it into the browser to see what is on the site. I would say you would pay no less than 10K for abc.co.za.
If I may make a recommendation, do a WHOIS lookup and send them an e-mail making a reasonable offer and see what they say. If they had the domain for a very long time and received no offers, they will probably be happy to get rid of it.