Need a "Mafia Wars" type game created

So I've been playing this game on a website that I will not name for at least 10 years now and they have somehow created a huge membership of 20M members on their site. The game is basically a remake of Mafia Wars on Facebook with a few extra things added to make it more personal. The way they have the game set up you can either spend 2 years building you player to complete the player or you can spend about $1,000 if you are impatient. These guys have 20M members and have them spending real life money on this game. I know people who have spent $10,000 on their players. There are thousands of people who spend money on this game like crazy. I want to recreate the entire site and do it my way. They've made a ton of changes to their site over the last 12ish years and a lot of the players don't like how the game ended up! How much would it cost me to have a coder create this Mafia Wars type game from scratch???