Textbox Value not set on Page_Load, but set by the time the page renders

I have a form with 3 textboxes that I create dynamically.
The 3 are txtAge, txtUnits and txtPrice.
txtPrice is set by getting a value using txtAge's value and multiplying it by txtUnit's value.
The controls are currently created OnInit (though I've tried doing it on Page Load and it doesn't change anything).
During my Page_Load method I find the textboxes using the unique names that I give them and when I check to see if they have a value, they are blank, however once the page loads they have a value just like I would expect them to.
For example if I change txtUnits from "5" to "4" and then cause a postback, on Page_Load txtUnits has no value but  by the time the page Renders the value is "4".
I thought the order went like this:
Page.Init
Page.LoadViewState
Page.ProcessPostData
Page.Load
Change events for controls
Server side validation
Button.Click or Button.Co ...