There are some good points here. I would definitely in the future separate your costs from your work. Hosting is their cost. It should have been paid by them up

There are some good points here. I would definitely in the future separate your costs from your work. Hosting is their cost. It should have been paid by them upfront, not from you. Its one thing you should require in the future. Not only will it weed out people who can't really pay, but it helps separate in people's minds what work you're doing. To your customers, that hosting cost is now included in their minds of what their site is "worth." It shouldn't be. Your work is separate, and the hosting costs have nothing to do with how much your work is worth. Mixing them up was a mistake on your part. You now have to prove what you did was worth $800, instead of proving that its worth $500, with $300 hosting costs (which would have been paid before this). I'd say stick to your guns, but also come up with a "carrot" instead of the sticks everyone else is talking about. Yeah, you might not think you need to, but adding in a few extra features to make sure you get your $500 might be worth it if you can pull them off quickly. And by carrot, I don't mean saying you'll do what you were going to do in the first place. To work psychologically, it has to be beyond what they were expecting.