sub cost {
    return $_[0]->get_price(PriceType->COST_ID);
}

sub list_price {
    return $_[0]->get_price(PriceType->LIST_PRICE_ID);
}

sub sale_price {
    return $_[0]->get_price(PriceType->SALE_PRICE_ID);
}

sub get_price
{
    my ($self, $id) = @_;
    return unless $id and $id =~ /^[[:digit:]]+$/;

    my $price_type = PriceType->retrieve($id);
    $self->_croak "PriceType ID ($id) unknown" unless $price_type;

    my $sth = $self->sql_find_price;
    $sth->execute($self->id, $id);
    my ($price) = $sth->fetchrow_array;
    $sth->finish();

    return $price;
}