Oh dear, I haven't counted in years but it know it's well between 1500-2000! My computer room is the pony room, we use it for nothing else, lol. I'm currently cateloging it since it's going into storage next may. It'll probably take me that long just to get through it all!
I know I have over 150 vintage MOC/MIB ponies. All the US released G1s except 20 or so with a bunch of UK and foreign exclusives. Nearly ever G3 up untill this core 7 crap started. And a MIB double up until the crystal princess line, after that I only got a double of the ones I really liked or exclusives. I love my varients but I gave up on those though I still pick up sweetie belles and starsongs when I can.
My model horse collection is starting to be good competition though! I must have 4-500 of those but when most cost between $30-$500 with a handful between $1000-$3500, that's kept me from buying everyone that's come out, hehe.
And no, I'm not rich! They're the reason I'm so broke, LOL. I have so much to sell it's not even funny. I sold 400 or so at the pony fair this summer and still took home over 600!