I.G.
If you are just starting, and don't know whether sewing is for you, I would say go inexpensive. I had an old Singer (maybe 30 years old) for years that could only sew straight and zigzag - no frills. That was fine for hemming pants, small mending jobs and the occasional simple project. When I was going to replace it, the new models just looked so cheap and flimsy that I took a leap of faith and got a Brother.
I am not a seamstress, I use it for small projects - I usually get fabric remnants and make toys or simple clothes for my daughter and hem my pants. I stayed in the $100 range for the machine (got a great deal on Amazon) and could not be happier. It has a lot more frills: attachments, stitch patterns etc.-I have had it for 2 years, use it a lot more than my old machine and have had no issues whatsoever with it.
It probably wont sew through 5 layers of denim... but I probably would never have a need for that anyways.
Bottom line: it depends on what you want it for. If you are planning to get into making more advanced garments or quilting, spend a bit more, if you're like me and just do the occasional little sundress or hem, a less expensive machine will be fine.
BTW mine is a Brother XL 2600 i, I paid $80 for it when it was on sale at Amazon.