```python
def stamp_table(dies: list) -> dict:
    table = {}
    for fragment, price in dies:
        if not isinstance(fragment, str) or not fragment:
            raise ValueError("Invalid fragment")
        if not isinstance(price, int) or price <= 0:
            raise ValueError("Invalid price")
        if fragment in table:
            raise ValueError("Duplicate fragment found")
        table[fragment] = price
    return table

def stamp_cover(label: str, dies: list) -> int:
    if not label:
        raise ValueError("Empty label is invalid")
    
    table = stamp_table(dies)
    
    n = len(label)
    dp = [float('inf')] * (n + 1)
    dp[0] = 0
    
    for i in range(1, n + 1):
        for fragment, price in table.items():
            if i >= len(fragment) and label[i - len(fragment):i] == fragment:
                dp[i] = min(dp[i], dp[i - len(fragment)] + price)
    
    if dp[n] == float('inf'):
        raise ValueError("No sequence of dies can spell the label")
    
    return dp[n]
```