how to create windows virtual machine with 16gb ra

I am totally new to cloud services, and using Windows Azure, I need a web server and a database server, each with 16gb of RAM. However, the extra large windows virtual machines only have 14gb of RAM. How would I go about adding 2gb of RAM to each of these servers, or do I need to do something else, such as incorporate a SQL database? I don't need to know the specifics of installation, all I need to know right now is what needs to be paid for, as I am just trying to figure out the price for everything. Thank you.

The Extra Large (XL) VM size provides 14GB available RAM. This applies to both Virtual Machines (IaaS) and web/worker roles (PaaS). There are no other VM sizes that provide more RAM than that. There's nothing you can do to add 2 extra GB.

UPDATE April 16, 2013: There are now two new sizes: 28GB/4-core and 56GB-8-core, available to Virtual Machines ~~(not for Cloud Services e.g. web & worker roles)~~. Announcement here. There's also a new SharePoint template in the Virtual Machine image gallery (since you mentioned using SharePoint) as well as a SQL Server template.

UPDATE APRIL 30, 2013: The new 28GB/56GB sizes are now available with Cloud Services, coincident with the release of Azure SDK 2.0 for .NET. Details here.

Just to add a bit, regarding web servers: Unlike on-premises servers where it's typically economical to buy the largest machine possible, it's better in Windows Azure to go with smaller VMs and have more of them. So, for a web server, go with the smallest VM size that would still run your software. Then, to handle additional traffic, scale to more web instances. As traffic ebbs, reduce the instance count. Load will be distributed amongst all of of the web servers (which are stateless - no user affinity to a specific instance).