According to the shop and what math skills I can muster, it would cost a grand total of $8,290 USD to hit VIP 20.
2 - 50pts = $10
3 - 100pts = $20
4 - 200pts = $40
5 - 300pts = $60 ($130 cumulative; a lot of players stop here as this unlocks VIP chests)
6 - 400pts = $80
7 - 500pts = $100
8 - 600pts = $120
9 - 800pts = $160
10 - 1000pts = $200
11 - 1500pts = $300
12 - 2000pts = $400
13 - 2500pts = $500
14 - 3000pts = $600
15 - 3500pts = $700
16 - 4000pts = $800
17 - 4500pts = $900
18 - 5000pts = $1000
19 - 5500pts = $1100
20 - 6000pts = $1200
Total ===== $8290