Who's wrong here & am I being unreasonable?

I sold something on amazon's website. I paid for postage on their site, I tried to retrieve the postage & could not do so, there wasn't an option to print. I contacted them, they said that if I had bought insurance then i could get my money back. By speaking with the postmaster at local usps I was informed that was a complete fabrication of their imaginations. So I look at this from a very basic business principle.....I buy it, you give it to me. Of course what it's going to come down to is (me being stubborn as I am) me telling them to be reasonable & fix this otherwise i'm not going to do business with them, at which point they will send me an email probably stating some legal mumbo & some prewritten garble about some user agreement (ya'll know what i'm talking about) and meanwhile the real person suffering here is the guy who bought my item, they don't seem to care about that either. So what's your thoughts, I just want to be given what I paid for & to them it's just not that simple, which blows my mind!