I find the watch's price quite reasonable. The base model G-Shock is US$100, while prime is US$140 (via RK), so the cost of the exclusive Prime-paint is only US$20 more.
Unless you'd rather go for this blue/red standard release version without the Autobot ensignia over the time and the word "Transformers" in place of "Casio": https://www.amazon.com/Casio-G-Shock.../dp/B00FMM6RR6