From the 2009/10 SPL Handbook. (Which you can download here)
C4.3.2 The tranches referred to in C4.3.1 are:
“The Basic Facility Fee Pool”, 48% of the Net Commercial Revenues, which
shall be shared equally amongst the Clubs participating in the League during
the Season in question; and
“The Supplementary Facility Fee Pool”, 52% of the Net Commercial
Revenues, which shall be paid to the Clubs participating in the League during
the Season in question in accordance with their respective league positions at
the end of that Season.
Basic Facility Fee Pool + Supplementary Facility Fee Pool = Total
1 4.0% 13.0% 17.0%
2 4.0% 11.0% 15.0%
3 4.0% 5.5% 9.5%
4 4.0% 4.5% 8.5%
5 4.0% 4.0% 8.0%
6 4.0% 3.5% 7.5%
7 4.0% 3.0% 7.0%
8 4.0% 2.5% 6.5%
9 4.0% 2.0% 6.0%
10 4.0% 1.5% 5.5%
11 4.0% 1.0% 5.0%
12 4.0% 0.5% 4.5%
48.0% 52.0% 100.0%
So as ye can see, it's pretty significantly weighted towards whoever finishes first and second.