If I had to guess, that cake looks like a 5-7-9-11.
There's not a whole lot going on with the cake that would warrant a huge upcharge other than the flower. The fondant is embossed with a lacy flower pattern, but that's it.
What is your base price for cakes? If it were me it would be $6/serving, but I know that not everyone charges that much. You have to think about your skill level and ability to pull it off (the cakes you have posted here are nicely done and I think this is something you could do easily). The edges are nice and sharp, so that would be important. If you don't have a base price for cakes figured out then that is where I'd start. Find out what it costs you per serving to make a cake. Include everything from ingredients to electricity to gas to pick up the ingredients... internal supports and fondant and everything. Once you figure that out, pricing cakes is a snap.