Price is going to vary significantly from $150 to $1500 depending on maker, magnication power, features, etc.
You have to decide what it's going to be used for - long range shooters tend to prefer 10X and up... plinkers and hunters "get by" most often with 3-9X.
There is a large amount of factors to consider... adjustable objective (AO), set parallax distance, click repeatability, brightness center and outside, reticle type, mil-dots, illumination, foggyness or ghost-images, quartering, fully sealed tube, etc.
What type and caliber gun will you be using? And mainly what type of shooting is involved? Those two questions will help most.