A 3-minute MP3 is roughly 7MB. A 3-minute FLAC is roughly 30MB. An entire 24-bit/96kHz At World's End soundtrack (approx. 2 hours) can take up nearly of space.
The primary way to obtain these soundtracks in FLAC is through high-resolution music platforms. Standard Lossless (16-bit/44.1kHz): FLAC Soundtrack - Pirates of the Caribbean