A question with no definitive answer. As stated it depends on TLD extension, the word itself, developability, recognition in other languages, length of word, word tense, etc.
For example, Health.com would be much more valuable than unhealthiness.com, even though both are technically one word .com domains. Skull.com would be more valuable than Tibia.com, because it is more recognizable and useful, even though both are just human bones.