I don't see it either in nutridiary or cronometer. Online searches show 60 calories for 100g.
http://www.buzzle.com/articles/dragon-fruit-nutrition-facts.html (has the most nutrient listing that I saw)
When I've tasted dragon fruit, it's been rather watery to me and 60 calories slightly high in that case. If you have really good ones that are sweet, take that into account and maybe in that case it is 60-70 cals.
Not too bad. I've found a place that has really nice ripe ones and I hope they're a lot sweeter than the ones I've tried previously. :)