The reason why geckos who look similar go for different prices is their line, and the person selling them. A new breeder obviously can't sell a gecko for $500. A breeder who's been around for a long time with a good rep can get away with selling one for a high price because of the quality of the breeder and the source. Prices of a gecko are affected in many areas... You mentioned yours has a yellow hue, but a big carrot tail. Many people don't like the yellow hue and would consider that a low quality tangerine, a brighter more vibrant orange body with a big carrot tail would be a great visual. Personally I think all SHTCTB's are fugly. I hate the color orange. With that being said I'm the only one out of everyone I've spoken to about leos that doesn't like orange on a gecko. Everyone seems to love orange on leos and I just don't get it. Other ways price is affected is by how new the genetics are, the genetic combination, how long it takes to make that visual, the breeder, the line, just about anything can affect a geckos' price.
Average eggs is a little hard to determine. Each female is different. Many people say first timers don't lay many fertiles. More often than not it's true, however, last year I had a first time female lay me 10 clutches (8 doubles, 2 singles), all but 2 eggs hatched. 16 babies from a first timer. Then I have a proven female, Claudia, who laid me 4 eggs her first season, 1 viable, and then her 2nd season lay me only 1 egg. Some will lay 3-4 clutches (groups of two), some will lay near 8 clutches. To answer your question determining the average is very difficult since many things come into play.
Sunglow vs Hybino is pretty weird... Sunglow was a name coined for a SHTCTB Tremper, then the first SHTCTB Bell was coined a Hybino (Hypo-Albino). They're the same thing genetically, just different albino strains. Now a days when purchasing one you'll need to ask them which strain it is specifically since many people are calling Trempers hybino's and bell's sunglows. The two are one in the same.