What is a domain worth? I guess that's kind of like saying, "What is art worth?"
I have registered many domains since the birth of the internet. In the beginning (1993) everyone registered domains through Network Solutions and it was $72.00 per year, per domain. I registered several domains at that price.
After a few years I was able to register domains for around $39.00 per year.
Today, registrars abound where you can register a domain for $9.95, and sometimes even less on sales.
But, What is a domain worth? I suppose it's worth whatever someone is willing to pay for it.
For example, I tried for several years to acquire my domain, pjhunt.com. I went through several variations before I was eventually lucky enough to obtain it. .cc, .ws, .us, .net and then .com.
I got lucky. I paid $9.95 for it. I doubt I would have paid $100.00 for it, but I don't think I'd give it up if someone offered me $10,000 for it.