For me, it was initially much more expensive to be Vegan than to be an omni, because I had to change out most of my pantry items, and I started using different spices, which can be expensive on the front end. Also, because I didn't know a lot about cooking Vegan, I ate a lot of prepackaged convenience items at first.
Now, it's actually much cheaper to be Vegan, and I purchase quite a bit of organic food. I can get organic dry lentils for 70 cents a pound, US, for instance, and a pound of dried lentils is a TON of food. In terms of over the counter remedies, I use a lot less than I used to, personally. Other than a very mild case of stomach flu in December, I haven't been sick once since going veg, and I use a LOT less pain medication than I used to because I don't get attacks of arthritus all the time, my back does't go out every other month, and I don't get menstrual cramps anymore. I don't need Tums anymore, ever. I feel a lot healthier as a Vegan overall.
Some things remain more expensive. Soy milk is quite a bit more expensive than cow milk, and I drink a lot more soy milk than I ever did cow milk. Other things are a lot cheaper. I get organic golden flax via mail order for like $3.50 US for a gallon container of whole seeds. They keep forever, don't require refrigeration and are the equivilant of dozens and dozens of eggs. In terms of household products, cruelty-free is a lot more expensive than P & G. However, I've learned a ton of new uses for distilled vinegar, which is only about 70 cents a gallon and a lot cheaper than the cleaners I used to use. And I've found a couple of brands of laundry detergent that seem more expensive until you read the label and realize that you only need a tablespoon instead of a cup per load.