While I agree with you 100% I think that this isn't a very good argument against lock-in. i.e what if Amazon pricing model changes making it not cost effective,

While I agree with you 100% I think that this isn't a very good argument against lock-in. i.e what if Amazon pricing model changes making it not cost effective, or what if they start limiting their services or what if a better service crops up and Amazon cannot compete etc... Lock-in is always an issue to consider regardless of how shiny those golden handcuffs are, end of the day they are still handcuffs.