Buy used/refurbished, or build from parts. That will save you a lot of money, even compared to newer towers that are on sale. Refurb with warranty is safe and economical. A 2-3 year warranty will catch the used parts that are going to fail soon. Building from parts is the cheapest but you will need to study it a little. It's not as scary as it sounds, modern computer parts fit together like a jigsaw puzzle. If you can assemble a bookshelf from a box kit, you can probably build a PC.
If you have any friends who are into computers and have built their own, ask them. If you don't feel confident that you could build your own computer, they will probably be glad to help. It's a hobby and to them building a computer is fun, even if they don't own it.