Well, if you want to place the Accumulated Sale Price or Regular Price next to Subtotal, that won't be necessary because the Subtotal is already the total computation of your line item on Page Load; however, if you only wanted to put the Regular Price and Sale Price on each line item, yes, that's very possible but it would need a modification on the ShoppingCart.cs. Here's the modification that you will need to apply to achieve this. Insert the highlighted parts on the DisplayItems method of the ShoppingCart.cs
Code:
tmpS.Append("<div class=\"shopping-details\"><p class=\"highlight\">" + GetLineItemDescription(c, ShowLinkBack, VarReadOnly, true) + "</p>");
tmpS.Append(AppLogic.GetString("showproduct.aspx.27", m_SkinID, m_ThisCustomer.LocaleSetting));
tmpS.Append(AppLogic.GetVariantPrice(c.m_VariantID));
tmpS.Append("<br />");
tmpS.Append(AppLogic.GetString("common.cs.64", m_SkinID, m_ThisCustomer.LocaleSetting));
tmpS.Append(AppLogic.GetVariantSalePrice(c.m_VariantID));