About $2500 on my 60g since I started in July. This doesn't include fish, corals, food, water. Albeit, I probably wasted several hundred dollars on equipment that my the LFS sold me when I started that I have since replaced (powerheads, lighting system)
In most hobbies, there is a diminishing curve, but as I continue my journey in this hobby, and keep learning more and more from experienced RCers, my spending has not leveled off as I'm continually looking to create the most hospitable environment for my 'pets'.
Initially, I did not understand the fascination with corals vs. fish. After adding a couple of 'token' softies, I'm now hooked on the beauty and the individual characteristics of these fascinating life forms. In the last 3 weeks, I've spent $800 on corals alone (thankfully my focus in on leathers, and LPS, I'll stay away from SPS so I don't go bankrupt.)
I do love this hobby/addiction and am completely HOOKED !