What is the traffic? Average betting amount, total traffic by volume, those things are really important because they represents how profitable your site is, and a potential buyer take it into consideration to calculate how many funds he may earn in X amount of time.
If you are willing to post this data over the internet then you may get a price estimation over here.
If the site was properly well done, well, at least it would have been something to consider since all the buyer will have to do is to work on the marketing to bring in more traffic but in this case, there is really nothing much to get from this and whoever would want to buy this will end up not giving much. You may need to make it catchy as it looks extremely simple for a provably fair betting site.