When you look at the top sites with lots of traffic, yup they certainly look great. But also you have to realize that there are hundreds (if not more) sites that have been unsuccessful in getting gamblers or have been shut down because of DDoS, exploits and hacks. It is great that you can code it yourself, but you have to factor in your time cost together with the future cost for hosting, marketing (in the form of giveaway and ads) and hiring support personnel, and also consider the risk of having unsatisfactory marketing results, legal troubles (if you are not living in a bitcoin-friendly location), bugs being exploited, DDoS, hacks, etc.