```python
def stamp_table(dies: list) -> dict:
    table = {}
    for fragment, price in dies:
        if not isinstance(fragment, str) or not fragment:
            raise ValueError("a die fragment must be a non-empty string")
        if isinstance(price, bool) or not isinstance(price, int) or price <= 0:
            raise ValueError("a die price must be a positive integer")
        if fragment in table:
            raise ValueError("die listed twice: " + fragment)
        table[fragment] = price
    return table


def stamp_cover(label: str, dies: list) -> int:
    if not isinstance(label, str) or not label:
        raise ValueError("label must be a non-empty string")

    table = stamp_table(dies)
    n = len(label)
    dp = [float('inf')] * (n + 1)
    dp[0] = 0

    for i in range(1, n + 1):
        for j in range(i):
            fragment = label[j:i]
            if fragment in table:
                dp[i] = min(dp[i], dp[j] + table[fragment])

    if dp[n] == float('inf'):
        raise ValueError("no sequence of dies can spell the label")

    return dp[n]
```