No idea how accurate or honest the figures are. But the list came from the USA (via P& and the SPL is only one of many leagues and many sports in the report. You can download the whole thing here and it contains some nice trivia.
http://www.globalsportssalaries.com
Probably the most remarkable thing is they thought the SPL was worth including as most Euro leagues and all South American leagues are omitted. Of the 333 teams covered, we are number 332.