why would 666.com be worth more than 50.com or 555.com?
imo 666.com wouldn't be worth more than 50.com but could be worth more than 555.com
666 means something as well as being triple NNN
(666 is the devil's number)
555 is just a triple NNN and rare.
Some may value the fact that it has another meaning as an added benefit. A bit like the difference between 12.com and 13.com (13 is an unlucky number)
50.com v 555.com imho I would always go for 50.com even if market value was the same. Both are rare but I'd prefer a shorter name over one that has 3 numbers the same. I think it's much harder to brand 555 than 50. Of course it depends on your site and target audience. 50.com would have an obvious market... 555.com less so. And if you wanted to target 555.com at a younger friendlier cool crowd, when not go for a word.com or a couple of made up words?
:?: