Laptop with an external device such as a Sony Erricson V640 (cost $600+ for the laptop + $300 for the cellphone)
IPhone 3G ~$1000
Not much to choose from, are there any other choices?
If you're limiting yourself to 10MB per day then I'm guessing you won't be doing a lot of browsing. Something like Opera Mini on any Nokia S60 device is a great mobile browser - or are you wanting a laptop to view sites full size?