Lifco, in theory, you have a very promising server - the actual design of it is flawless.
But you need to re-adjust the ways you run it. Firstly, you shy away from criticism way too quickly. As it is in real life, the customer always being right, is the same logic for private servers. If you don't appeal to them as a GM who values their individual opinions then they will leave. Ideally, you should be introducing ways to interact with the community on improving the game.
Secondly, this current event is horrendous. Within 30 mins of hunting hens, I acquired 1 million cash, a BD-Slayer and half a dozen day-scrolls. Before the event, gold had quite a reasonable value and 1 million would have got me an awful lot of mid-level items - now it won't. I was even shown level 48's armors by quite a few people, not to mention a tele ring dropped - all in two days of this event.
Lastly, you can't use the arguement of 'i'm running a free server so stfu and enjoy.' We have criticism, we have opinions and we, as the customer, form your player-base. I think the dropping of it from 30-35 average peak time to 20-25 is testimony that you really need to address the economical & relationship factors within the game.