I attended BC2013 and I ended up spending more at the vendor's than I had planned. Plushies can get expensive ($~2000.00 for a very big one), but I got a Twilight (non-princess) and pinkie (high quality) for $150.00. The Bronycon plushies were $25.00 each, if I remember right. The first vender you'll probably want to visit will be the SugarCube Corner (We Love Fine). which will have a big line from the start of day one to the end (t-shirts will be $25.00+). If you need a 2x or 3x t-shirt you'll need to get there on day one to make sure you get what you want. If you wear a medium or large you might be able to wait until day two when the line gets a little smaller (I recommend you get in line and get what you want on the first day). Some items are cheaper on the internet than at the con and some items are dirt cheap on the last day of the con (plushies and t-shirts are not discounted, because they just take them home and sell them on the internet). Pictures, and things like that could be 2 for 1 on the last day (remember that's 2 for 1 of what's left, you won't have a choice at that point). All that having been said. Don't worry about how much you have to spend at the vendors. That isn't what it's all about. BC2013 was my first con of any type and it was the best thing I've done in my life (I'm 40). I'm going again for 2014.
FireFox
p.s. Bring your own water, soda, sports drink, etc. and make sure you have plenty with you when you leave your hotel for the day.