The truth is that garage door openers are simple and similar.  Their are various features and some quality difference that explain the pricing difference.  For almost every residential door a 1/2 horsepower opener is plenty of power in spite of the marketing you see featuring 1  and 1.5 horsepower openers.  The market has been dominated by the Genie and Liftmaster/Chamberlain/ Craftsman companies since the beginning.  Each makes an array of models and have a PROFESSIONAL  and a retail line of products  with the professional line featuring sturdier bult, none snap together solid rails and longer warranties.  The features that change the price are

• Professional vs retail line for quality and warranty

• Belt drive vs chain drive 

• Solid one piece rail vs snap together sectional rail

• Wi-Fi / smart phone control

• remotes and keypads required

• power where required

• height of garage doo