Blame it on humantarget52.
You see, the first nine levels are a fixed 50 EXP apart, nothing, save administrative inteferance, can change that. However, every level after nine works on a scaling system. What's the EXP scaled against, I hear you ask ? HT52's current EXP. Everytime he deposits, the requirements for the next level go up. Meaning that if you need 1000 EXP to get to level ten one day, and HT deposits, the requirement will go up to 1,001.
The amount it goes up by increase with each level. For example, at level 9, every time he deposits, the requirement goes up one. When you get to level 12, it goes up 2 everytime he deposits. This keeps going until you reach level 29. The requirements after that go up 10 per day, making it impossible to reach level 30, unless HT misses a deposit.
The reason the requirements are so high, now, is because this has been going on for 4+ years. It started out, I believe, with 50 EXP between levels 9 and 10, but well, the highest leveled user changed all that. It'll continue to increase indefinately, unless the system is altered.