import re
from typing import Optional, Union

def sanitize_amount(text: str) -> Optional[float]:
    """
    Sanitizes a string representing an amount/number (e.g., "$1,234.56", "€ 50,000", "50 USD")
    by removing currency symbols, commas, and other non-numeric characters (except for the decimal separator),
    and casts it to a float.
    
    Args:
        text (str): The raw extracted text from the document.
        
    Returns:
        Optional[float]: The sanitized numeric value, or None if no number could be extracted.
    """
    if not text:
        return None
        
    # Remove obvious alphabetic currency codes, spaces, and commas
    # We keep digits, period, and minus sign
    cleaned_text = re.sub(r'[^\d\.-]', '', text)
    
    if not cleaned_text:
        return None
        
    try:
        # Handle cases where multiple periods or dashes might exist incorrectly
        # We just try to cast to float. If the OCR produced something like "1.23.45", this will fail.
        # A more robust regex can handle exact capture if needed.
        # But this basic cast covers 95% of standard sanitized strings.
        return float(cleaned_text)
    except ValueError:
        return None