Is this what you want? Sorry, but your speccs are not very clear ...

2A2B2C = 28.423828125
4AC = 5.315625
ABC = 2.165625
BC = 2.8875
[download]

This was produces by the following code (adapted from holiy's solution):

use strict;
use warnings;

my @p = (1.5, 2.5,  3.5 );
my @m = (0.5, 0.55, 0.60);


sub calc
{
    my $i = shift || 1;

    my $idx = ord(shift)-65;

    return $m[$idx] * ($p[$idx]**$i);
}

for my $str (qw/2A2B2C 4AC ABC BC/) {
    my $res = 1;
    while ($str =~ /(\d)?([A-Z])/g) {
      $res *= calc($1, $2);
    }

    print "$str = $res\n";
}
[download]