agreed, and you have many options.
weighted keys - feels more like a real piano, but also costs more.
# of keys - 64 or less to the full 88, more keys costs more but gives more dynamic range (although you can also use transposition features to get that range.
# of synths - many keyboards now have patches that make them sound like other instruments, the range and quality of these also is a factor in price.
pitch and volume wheels - used for effect, these thumbwheels add to versatility and expression
stand - if your keyboard is the flat type, you might want to buy a stand for it. if it is a piano type, you won't need one, but these cost more as they appear to be pianos. they are also less mobile being heavier.
construction - has a factor in cost
disk drive - raises cost significantly, used to add a lot more synth patches to the keyboard.
overall tone - not all keyboards sound the same. some have much fuller tones and response
pedals - used for reverb and other piano effects
