def sanitize_price(price_str):
    """
    Normalise a price string and convert to float value.
    :param price_str: Price string to normalise.
    :return: Float price value.
    """
    if price_str is None:
        return None
    price_str = price_str.strip('$ \t\n\r')
    price_str = price_str.replace(',', '')
    return float(price_str)