There is a considerable difference between Male and Female Gecko prices. Due to Females of most species being more sought after as people just figure that they can create trios rather than sell an excess female, this makes the price go higher.
Male U.Milii- $70-$80
Female U.Milii- $100-$130 (maybe even more)
Obviously prices depend on colour, age, health etc.
It is practically impossible to tell sexes from hatchling Geckos. Though, People have said that a large number of clutches do end up resulting in a 1.1 ratio in hatchlings.
Once a pair have successfully mated, It takes around 4-6 weeks for the eggs to actually be laid. 4 weeks for the smaller species (Diplo's, Gehyra etc), 5 weeks for medium sized (Underwoodisaurus, Nephrurus, Phyllurus etc) and 6 weeks for the larger species (Saltuarius, Oedura, Cyrto's etc). If incubated appropriately at a nice set temp, eggs will take (U.Milii) around 6-8 weeks.
Shawn