I believe it is cheaper to buy. You can get a lot of really good buys on clearance at the end of each season! When making clothes you would have to have so many different materials to make a variety for your wardrobe.
I have found that quite often, sewing is more expensive unless you come across a great deal on sewing supplies. Finding quality fabric can also be an expensive challenge. The exception would be if you're looking at a high-end garment at the store (evening wear, etc) - you may save money sewng.
It depends on the article of clothing in question. If you all ready have the pattern to make something, it is sometimes cheaper depending on the fabric you use.
It is actually cheaper to buy clothes. The companies that make the clothes buy everything in bulk and usually pay the workers almost nothing. So in reality they are doing what you want to do but doing it a lot cheaper.
That depends where you'd buy clothes from. It would certainly be quicker to buy them, and if you buy from a place like WalMart or Target you can get cheap clothing. However, if you are very talented, you will be able to make higher quality, nicer looking things for cheaper.