Not sure if this has already been discussed recently but eh...
So, are you the type that can contain yourself and got exceptional accounting skills? Or do you go nuts when you see merchandise that's of your favorite character and/or anime?
"Tʜɪs ɪs ᴀ ɢᴀᴍᴇ," ╔══════════════════╗ x I normally try to stay under 50 bucks. But I spoil myself it is one of my favorite characters or series. x ╚══════════════════╝ "ʙᴜᴛ ɪᴛ's ɴᴏᴛ ᴊᴜsᴛ sᴏᴍᴇᴛʜɪɴɢ ʏᴏᴜ ᴘʟᴀʏ."
I buy very little merchandise these days, because I just don't have the space. I do still collect art books and recently spent a little over $100 on Kim Jung Gi's 2011 Sketch Collection, which is freakin' awesome.
For a series I tend not to buy plushies or keyrings, etc and so money can be spent on better figures, manga, and dvds. Generally I think around £200/ $320 to be generous for conventions and events for several series. But I only really go to two events a year and don't shop online for these types of things.
I like a good bargin and I don't just buy the first thing that has my favourite series name on it. I like buying unique looking figures for a good price, despite not knowing about the series. I tend to love the series afterwards.
I usually save up a crapload of money throughout the year and then spend it on whatever my heart desires.
My limit is usually $100 on any one thing, especially if it's a figure or something. Amiami's kicking my a** with how much it is to import a game.
I try really hard to limit myself to absolutely no more than $100 an item, and even then I hate spending that much. My older boxed sets are sadly in the $150 range because they were purchased before compressed packaging or whatever =_=.