Abnormal data consumption when downloading files from Apple

(Apologies if this isn't the correct forum, I wasn't sure where else to post it).

In recent weeks I have been noticing abnormally high data usage when downloading files from Apple. I first noticed it in September when I tried to download the September event podcast, and most recently today when downloading Yosemite. Both days were work days for me so, save for maybe a gig or 2 of web browsing and other general traffic, these were the only downloads I initiated. The September event, a ~2GB video file, ate up nearly 50GB of my broadband quota - the Yosemite installer, at ~5GB in size, has eaten up just over 15GB of my data.

I have also noticed these downloads are slower than usual. At first I attributed it to the demand on Apple's servers (especially today with Yosemite) but last week I tried again to re-downloaded the September event podcast and noticed similar performance. Other large downloads I have done lately do not exhibit these issues, only these files from Apple, yet I also have an Apple TV and have noticed no problems streaming 1080p movies and TV shows.

I'm in Australia - is anybody else (here or elsewhere) noticing similar issues?