How about adding gold to it, on weekends (weekend scratch and win) or just for holidays. (Holiday Scratchers)
Weekend suggestion. Holiday
1 bar = 2 gold...................5 gold
2 bars = 4 gold................10 gold
3 bars = 6 gold................15 gold
4 bars = 8 gold................20 gold
5 bars = 10 gold..............25 gold
6 bars = 12 gold...............30 gold