Massive Reggae Hits might be it
Ensiferum have released 5 studio albums. They have also released a compilation which is made up of their first three demo albums. So in total they have released 6 albums including this compilation.
Weird Al Yankovic has released 13 original albums, as well as 6 compilation albums.
Teena Marie released 13 studio albums and 7 compilation albums.
Ultravox have released eleven studio albums since they formed in 1975. In addition to that they have released four live albums and a number of compilation albums.
You're talking about compilation albums. They're sold on various websites, but, as far as I know, there isn't a website or label dedicated specifically to compilation albums for Metal bands. Dwell Records has composed a number of compilation tribute albums, and many labels will compose their own compilation albums as a sampler of the bands they have in their lineup.
alice cooper had 26 studio albums, 46 singles, 10 live albums, 21 compilation albums, 12 video released and an audiobook.
In Harmony - compilation albums - was created in 1980-10.
The Angelic Upstarts have released 12 studio albums, 7 live albums, 10 compilation albums and 1 DVD. They have also released 19 singles since they were founded.
Other compilation albums of Westlife was created in 1999.
The Veronicas have released six albums, including three studio albums, two live albums, one compilation album. Their studio albums include The Secret Life of, released in 2005, Hook Me Up, released in 2007, and Life on Mars, released in 2013.
Modest Mouse have released many albums in the duration of their career. They have released five studio albums, two cassette albums, six ep's, two compilation albums, and two live albums.
if by that you mean how many released about 15 official albums and 6 compilation and specialty ones