When copying Condition Item Details from one Bid to another, the Condition Unit Costs and Totals may be different. That's because only the Condition Item Details (the Rows) are copied over, the Markups and Indirect Expenses are not copied from the original Bid. Markups and Indirect Expenses must be setup individually in the new Bid (this is by design to avoid changing the receiving Bid's Markups/Indirect Expenses setup).
When copying Condition Item Details from one database to another, any information (Item Types, Payroll Classes, etc.), not already in the Master Tables of the destination database, is automatically added. If the option to "Create Master Items during Bid copying" is selected (Tools > Options), Quick Bid adds each Item to the Master Items list also, if it doesn't already exist.