How much does the price change between each iphone release?

I'm thinking about getting a iphone but since the month for the usual new release is just a round the corner I'm wondering if I should wait or if the price is going to get a lot higher and I should buy now.

Added (1). To clarify, I'm asking about the price from the apple store solely not the price from different plans.

Iphone 5s cost two orphans now. I believe when the Iphone 6 comes out the cost of the iphone 5s will be at only 3 homeless dogs. I think you should wait.

Yes, 6 is going up. Market price wise, a new 5s 16gb right now is $650. Expect the base 6 to run $750-800. So the contract price will probably bloat as well. Some reports says even $900 and beyond.
http://www.techradar.com/...rs-1099865
But the 5s will be a lot cheaper on contract. Probably $100-150.

Best luck.

It doesn't. Since 2008 Apple has released the iPhone on a $199, 299 (2 year contract plan). Included $399 when they started selling 3 varying (size) models.

As far as the rumors of increasing prices for them, what is expected there's that the 5.5" iPhone 6 would be the one to have these increases.

So I expect it to be

iPhone 5s - $99 (16GB), $199 (32GB)
iPhone 6 (4.7") - $199 (32GB), $299 (64GB)
iPhone 6 (5.5") - $299 (32GB), $399 (64GB), $499 (128GB)