I would like something like this as well. I have searched around for ages, for a good working (Ajax) form with price calculation based on various options and so on. And where pricing can be per 3 months or yearly basis. However nothing comes even close sigh.
I even hired a freelancer however after spending 150 USD on the script and his time, he provided me with a very basic unfinished script. Sigh.
So if anyone knows of a script which could do this, I would be grateful.
As an example I would like to mention something like this: http://demo.whmcs.com/order/
It looks excellent. Just try it out and see how the form works. I would recommend trying to order a Dedicated Server, than you will notice all the options. Among them are real-time domainname check, billing cycle, coupon codes, configuration options, etc. And the best of that script, is that it calculates the price on the fly.
The downside of this, is that it’s part of some expensive automated webserver script. Sigh.