Not too pretty, but here you go:
switch(r, 1, 30, 2, 24, 3, 30, 4, 16, 5, 14, 6, 12, 7, 10, 8, 8, 9, 6)
* if(defaultBuyinFee < 20, 2, if(defaultBuyinFee < 35, 2.5, if(defaultBuyinFee < 60, 3, if(defaultBuyinFee < 120, 3.5, if(defaultBuyinFee < 180, 4, if(defaultBuyinFee < 250, 4.5, if(defaultBuyinFee < 500, 5, 5.5)))))))
* if(n < 11, 1, if(n < 21, 1.5, if(n < 41, 2, if(n < 71, 2.5, if(n < 101, 3, if(n < 151, 3.5, 4))))))
Using your example, here's what the awarded points look like:
1: 300.00
2: 240.00
3: 300.00
4: 160.00
5: 140.00
6: 120.00
7: 100.00
8: 80.00
9: 60.00
10: 0.00
11: 0.00
12: 0.00
13: 0.00
14: 0.00
15: 0.00
16: 0.00
17: 0.00
18: 0.00
19: 0.00
20: 0.00
21: 0.00
22: 0.00
23: 0.00
24: 0.00
25: 0.00
26: 0.00
27: 0.00
28: 0.00
29: 0.00
30: 0.00
31: 0.00
32: 0.00
33: 0.00
34: 0.00
35: 0.00
36: 0.00
37: 0.00
38: 0.00
39: 0.00
40: 0.00
41: 0.00
42: 0.00
43: 0.00
44: 0.00
45: 0.00