You're asking a question that has no real simple answer. Crested gecko value is based on the eye of the beholder, which means if you want a general price range and to know whether or not anybody is going to be genuinely interested in your animals, you'll need pictures of all of them.
Females are generally more expensive than males, for obvious reasons. Males are typically worth half as much as a female of equal color, pattern, and structure, unless that male just so happens to be so freaking incredible that his genes are worthy of passing around amongst your whole colony, in which case they are worth as much as you think you can get out of him.
On average, you can expect an unsexed flame/harley of no groundbreaking pattern, color and structure to go from anywhere between 30 to 75 dollars. Now, this isn't some kind of national average. Prices don't typically go lower than 30, but value can definitely go above 75. Factor in whether or not it's got a tail... Usually, the tail devalues the gecko by about eh. 15 to 20% I would say, but again, this is usually a moot figure when attempting to apply to a "grade A" specimen. Keep in mind, you are competing with PetCo and their prices for their geckos. A lot of people get some great bargain deals out of PetCo, and I personally have walked out of PetCo's with animals twice as nice as what you've posted here. I'd be competitive and ask yourself if you'd really buy something for 100 bucks what you could buy for 50 at a petstore without paying shipping on it either. The juveniles you have posted are nothing to really shake a stick at... not to diss what you've got, but I'd pay 40 to 50 bucks at best for any of the juvies you've got there.
For an adult pair, unless your male and female are both nice creamsicles, blonde harlequins or red harlequins, your asking price of $500 is maybe a touch high. Well, a lot high. A patternless of color (IE, not brown or olive, yuck) female would sell for probably 150 dollars, and a male of her same variety would sell for maybe 80 bucks. Just to put that into perspective.
Anyway, that's my take on it. Keep in mind, many individuals who purchase crested geckos for their collections are doing so with very discerning taste. While generally there are "hot sellers" like pinstripes and red harlequins and the like, a lot of people have standards, and if that gecko's pattern doesn't reach all the way up to the dorsal and the ground color isn't firetruck red, it's not worth the asking price of a standard high quality red harley. You'll need to basically aim high and if you get no bites and really need to sell, reduce your prices until somebody bites.
