When Samantha paid $300 in 30 equal monthly installments, she paid a total of $<<300*30=9000>>9000
Since the higher purchase is a deposit plus the total monthly installments, Samatha paid $3000+$9000=$<<3000+9000=12000>>12000 for the refrigerator on higher purchase.
If she would have bought the refrigerator on the cash prize, Samantha would have paid $12000- to $8000= $<<12000-8000=4000>>4000 less.
#### 4000