If you have a paid Dropbox account, you just received an unexpected bonus: twice as much storage at no extra cost.

Cloud storage provider Dropbox last night doubled the amount of storage that Pro subscribers receive, increasing its Pro 50GB and 100GB packages to 100GB and 200GB, respectively. The larger storage allowances have already taken effect.

The official Dropbox announcement makes it sound like the cloud storage company doubled its paid allotments as a customer service: "We've heard from architects with giant drafting files and photographers with huge portfolios, but mostly we hear from families who have more than 100GB of photos, docs and videos."

Perhaps those cloud-addicted families inspired Dropbox to double its storage allotments, but methinks marketplace realities played a large part in the company's decision. A quick comparison shows that Dropbox's prices are coming under intense pressure from very big players. For example, Google Drive runs under $60 per year for 100GB; Microsoft's SkyDrive comes in at $50 per year.

By contrast, Dropox's 100GB package runs $9.99 per month or $99 per year; the 200GB package is $199 per year. In addition, Dropbox announced a new 500GB package at $499 per year. Dropbox's Team package -- which includes administrative tools -- remains unchanged at $795 for up to 1TB and five users.

Granted, there are some service differences: SkyDrive, for example, limits files to 2GB and Google Drive tops out at 10GB. Dropbox can take files of any size if you upload from the desktop app. All three services have Windows, Mac, and iOS apps, and Google Drive also runs on Android (you thought otherwise?); Microsoft's SkyDrive also runs on Windows Phone; and Dropbox is also available on Linux, Android, and BlackBerry.

While I'm not one to look a gift horse in the mouth, perhaps Dropbox's bonus is not so great after all: When it comes to bytes for the buck, Dropbox is still roughly twice as expensive as Microsoft or Google -- even after the doubling down.

This story, "Dropbox doubles down on storage," was originally published at InfoWorld.com. Get the first word on what the important tech news really means with the InfoWorld Tech Watch blog. For the latest developments in business technology news, follow InfoWorld.com on Twitter.