Customers ask us this question often, and the answer is that a lot of elements contribute to the pricing of a Windows based virtual server.
First, and most obvious, are the Microsoft licensing fees involved. Windows isn't free like Linux, and through an SPLA contract, also known as a Service Provider Licensing Agreement, Microsoft offers their products to service providers like us on a perpetual monthly fee basis. And thus, we pass on that cost to the client.
Another factor is the disk space utilized by Windows. While a typical Linux operating system takes up about 3 or 4 GBs of space, Windows takes about 15 GBs of space on average. Multiply that by thousands of VPS, and you can see how expensive SSD data storage can be to just host Windows virtual servers. And because we use a distributed storage cluster, where every block of data is stored three times for redundancy, then it becomes three times the storage space needed.
The large SSD disk storage requirement is the biggest contributing factor to the price of a Windows VPS.
Last, Windows requires more RAM, and thus, you need to deploy a virtual server with more RAM than a typical Linux virtual server would need.
Maybe someday Windows will shrink down in size, perhaps the pricing of enterprise SSD storage will be extremely low, or Windows will go open source, and we will no longer need to charge more for a Windows VPS.
In the meantime though, we will always try to optimize our costs as much as possible and we will pass on those savings to you.