Now that's a tough question. There are so many points to consider. I will say that, in today's market, there are some very good, great value scopes out there. I tend to just cateorgize them into three groups:
1) Cheapos (usually Chinese crap, sometimes Philipines) such as Barska, BSA, NC Star, etc. I don't care to own or use these at all.
2) Mid lines. These are typically very good optically, and are (more often than not) priced at a good value point. At the upper range of these I'd include Zeiss Conquests, Bushnell Elite 4200 and 6500, Sightron Big Sky, Nikon Monarchs, Leupold VXIII and above, Burris Sig Selects, Trijicon, etc. These will usually do ANYTHING required in most hunting scenerios. Well worth using IMO. There are some others in here that I would consider O.K. but nothing to write home about. We're talking about ones like Burris FFII, Nikon Buckmasters, Sightron I and II, Leupy I and II and Rifleman, etc.
3). The uppers. These are wonderful instruments and very expensive. The fancy Zeiss', Swaros and S & B's are a joy to use. I'd place the Kahles C series close by also. Are they worth the extra $ or are they 2X or 3X as good. NO. Should you use them if you want or can afford too... DEFINATELY. Nothing worse than to see a $1500 + rifle with a $100 scope. Just gross IMO.