my %money_spent = ();
foreach my $customer (keys %myHash) {
    $money_spent{$customer} = $myHash{$customer}->{"money"};
}

##</code><code>##

my $money_spent = 0;
foreach my $customer (keys %myHash) {
    $money_spent += $myHash{$customer}->{"money"};
}

##</code><code>##

my %money_spent = map { $_ => $myHash{$_}->{"money"} } keys %myHash;

##</code><code>##

use List::Util qw/sum/;
# ...
my $money_spent = sum map { $myHash{$_}->{"money"} } keys %myHash;

##</code><code>##

my %myHash = (
    "Fred Flintstone" => {
        "money" => 1000,
        "wife"  => "Wilma",
    },
    "Barney Rubble" => {
        "money" => 2000,
        "wife"  => "Betty",
    },
);