Pay them what you owe them and move on. If you don't like their policies, don't buy from them.
I absolutely disagree and commend the OP on bringing this up.
Like many, many people (I would venture to say the vast majority) would be incensed to find myself in a similar situation. The suggestion by Halcyon that most people would just say thank you and pay up is, I believe, offensive. That they should obstinately stand by such a policy in the face of this conversation is, similarly, offensive.
Diving is an expensive sport, we all accept that. That said, I can't simply afford a random $400 bill I wasn't expecting without batting an eye. I do have a budget. If that budget allows for boot replacement now and, perhaps, a zipper replacement later, well... that's what I can afford, isn't it? If I found myself in the position of the OP... I simply don't know what I would do.
I reiterate my thanks to her for bringing this up so that others might not run the risk of falling victim to the same behaviour.
I think we all know that Halcyon makes some top-notch products. Many of us (myself included) have stories about great customer service. But just because they do a lot right doesn't mean they're immune to doing wrong. And this whole story is one HELL of a wrong.