IMO, $50-$100 for a light is the sweet spot, in terms of value for money. You can certainly get lights cheaper than that, but in general they will have poorer quality build, UI, tint, beam profile, etc. A flashaholic probably wouldn't be happy with them.
There are also lights that are much more expensive than $100, and usually are better quality, but you're paying for a marginal increase in quality. Unless you've got money to burn, or absolutely must have the best of the best, they don't offer good value.
And, of course, you can buy a $50 Maglite, and be very unimpressed. So, do some research on brands and models, and pick something in the $50-$100 range. That's what I do. My favourite brands are Zebralight, Armytek, Sunwayman, and I used to like 4sevens (but no longer like them because they've gone a different direction).
I also have some cheaper lights, some of which are of decent quality, but they don't get a lot of use.