Displaying total cost of prices from a table
First, I would switch from using eval to parseFloat, since it appears that eval provides no extra features and allows arbitrary code to be executed unless you just happen to have values other then numbers in total_item_price tds. 

Second, since you are performing no extra processing with prices_array, it would be better to skip the array altogether and combine:

 var prices_array = new Array(); // Where our prices are held
 // For each .total_item_price - a &lt;td&gt; within my table.
 $(".total_item_price").each(function(){
     var text = $(this).text();                   // Get the value
     var prices = text.substring(1, text.length); // Format it into a string
     prices_array.push(prices);                   // Push it onto our array
 });

 var result = eval(0);
 //  Add up our array
 for(i = 0; i &lt; prices_array.length; i++)
 {
     temp = eval(prices_array[i]);
     result += temp;
 }


into (with result renamed as totalSum for readability):

 var totalSum = 0;
 // For each .total_item_price - a &lt;td&gt; within my table.
 $(".total_item_price").each(function(){
     var text = $(this).text();                   // Get the value
     var price  = text.substring(1, text.length); // Format it into a string
     price = parseFloat(price);
     totalSum += price;
 });