There are so many different variables when it comes to buying optics for a weapon. You need to know what your going to be using the weapon for before you start choosing optics.What works good for home defense/close quarter work,doesn't work well for other things,just like a long range set up doesn't work well for up close work.
For hunting,it depends on the type of terrain you will be in. Thick brush/wooded area's don't need high magnification,while hunting out in the open desert/open fields it comes in handy.
Then,The price range for optics runs from under $100 to $5000+. And in that,you actually do get what you pay for.
With the cheaper optics you get cheaper internal components,cheap lenses,and they usually don't last to any type of abuse.
Most people spend $200-500 on optics,and are very happy with them.They have decent lenses/internals,but most lack the clarity of higher priced units.
Scopes in the $500-750 range have better lenses/coatings/and internals,and are great all around scopes for hunting/target shooting.
The $750-1000 range everything is very good with these optics,but they are still not top shelf. This is also the beginning price range of decent Long Range scopes.
From $1000- 2000 scopes,your paying for all the little extras that have been put into these optics like Zero stop,Tactical tuurets,fancy reticles,and the top end components that come in these scopes. These optics are very good,and will serve the most demanding shooter.
After you go higher, the $2000+ scopes are the highest quality components available,and these are the cream of the crop for Hunting/Tactical/Benchrest shooters. If you are a serious competition shooter,professional hunter,or make a living with a weapon,these are what they want on their weapons.