This kind of thing pops up now and then. Basically, what you are saying is that whatever is in the product table at the moment is what goes in the quote, after which the copied information may (probably will) diverge from the product table.
Establishing a relationship is possible for certain cases - such as the hypothetical case of being asked to UPDATE the quote with more info, in which case you would have the chance to reset the costs. For that reason, having some relationship is at least potentially possible.
However, the issue here includes that you need a point-in-time capture of the current data at the time of the quote. This is a case where you probably would copy data from the product table to the quote table. I don't know about using a copy of the record so much as somehow doing an INSERT INTO for the records you need to reference. Since you didn't mention how you built the quote (in the mechanical sense of what steps you take for each line item), I cannot give you more directed suggestions at the moment. But I can confirm that it SOUNDS like a legit case of copying data. I cannot confirm whether a relationship would be good or superfluous because that would depend on details of your business model that were not mentioned in your question.
Hope this is responsive enough for you.
Doc-Man, this is exactly what I am looking for. Finally, somebody gets it!

Ok, so do a INSERT INTO query, then maintain some type of relationship for the update at a later point. Here's the mechanics of quote entry.
1. Open quote form to new record, fill in all pertinent data for main quote info
2. Each quote detail (line items) will EITHER a. Lookup a product from the product table or b. create the data on the fly by user entering description, qty, and price(no corresponding product).
3. I need to be able to edit the product from the quote detail line and modify and save or cancel, then if saved, re-enter new price, if cancelled, keep original price from step 2 above.
So with that being said I guess I need a field in the quote details table that can, if necessary, relate to the product ID to re-lookup.
Does that sound like what you are referring to?
Then of course a buttom on the main form that could update all items if quote needs updating due to customer coming back after "quote good for date" and re-questing pricing update.