How much does is cost to buy an iPhone 4 or 4S on pay as you go?

How much does is cost to buy an iPhone 4 or 4S on pay as you go?

There are no discounts for pay as you go at most of the carriers. So full price:
$599 for 4s and $450 for 4.

Depends which provider you buy your phone from. In the UK, usually O2 have good deals, especially on Pay as You Go but unfortunately I can't advise on anywhere else.

I took the risk of buying an White iphone 4s on ebay for like £330, got myself a mini sim and it works fine. I've had it since last may.

£330 from CPW for the iPhone4 and £430 for the iPhone4s.

I'd personally recommend the iPhone4s over the 4. The 4 is now about 2.5 years old and support for this handset is beginning to fade. Shortly it won't be receiving iOS updates, which means you'll find many of the apps you want won't be supported any longer.