Database structure is the following:

id|metaKey|metaValue
--+-------+-----------------------------------
55|product|a:8:{s:3:"sku";s:0:"";s:8:"products";a:3:{i:1;a:3:{s:6:"option";s:1:"1";s:5:"price";s:5:"14.95";s:9:"saleprice";s:0:"";}i:2;a:3:{s:6:"option";s:0:"";s:5:"price";s:0:"";s:9:"saleprice";s:0:"";}i:3;a:3:{s:6:"option";s:0:"";s:5:"price";s:0:"";s:9:"saleprice";s:0:"";}}s:11:"description";s:124:"Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.";s:8:"shiprate";s:1:"A";s:8:"featured";s:2:"no";s:4:"sale";s:3:"yes";s:10:"cart_radio";s:1:"0";s:6:"optset";s:0:"";}

This really is from the wordpress site, I have to retrieve the very first "cost" value that is 14.95 what's the easiest method to retrieve a particular value from the serialized array saved in mysql?

Create query, read data from SQL, unserialize() metaValue and can get on as an array. You may also use regular expressions if you want to extract it inside mysql, but that is a not so good approach.

Use unserialize() to retrieve the metaValue data.

The next code can retrieve the very first cost value:

$result = mysql_query("SELECT * FROM tbl WHERE id=55");
$row = mysqLfetch_assoc($result);

$serial = $row['metaValue'];
$data = unserialize($serial);
echo $data['products'][1]['price'];

The information within this row is structured as:

array(8) {
  ["sku"]=>
  string(0) ""
  ["products"]=>
  array(3) {
    [1]=>
    array(3) {
      ["option"]=>
      string(1) "1"
      ["price"]=>
      string(5) "14.95"
      ["saleprice"]=>
      string(0) ""
    }
    [2]=>
    array(3) {
      ["option"]=>
      string(0) ""
      ["price"]=>
      string(0) ""
      ["saleprice"]=>
      string(0) ""
    }
    [3]=>
    array(3) {
      ["option"]=>
      string(0) ""
      ["price"]=>
      string(0) ""
      ["saleprice"]=>
      string(0) ""
    }
  }
  ["description"]=>
  string(124) "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
  ["shiprate"]=>
  string(1) "A"
  ["featured"]=>
  string(2) "no"
  ["sale"]=>
  string(3) "yes"
  ["cart_radio"]=>
  string(1) "0"
  ["optset"]=>
  string(0) ""
}