Perhaps it's a matter of perception. The way I see this, if you gave away all 20 coins, there was a cost to that generosity, ie., how much it cost you to buy the whole lot. Similarly, if you gave away 19 of 20 coins, keeping just one, there was still a cost to the giveaways, represented by the value of those coins. To my mind, if you can determine distinct values for each individual coin in a lot, you can assign them proportionate costs as well. Whether or not you do that is of course a personal choice. I can see how for some collectors, this book-keeping option is not a practical necessity and probably just a waste of time, but just speaking for myself, seeing a line in my spreadsheet recording that a garden variety Tetricus I has an identical cost to a denarius of Otho from the same lot is disturbing beyond my level of tolerance. Of course, if we're looking at a group lot of say 50 LRBs with an average cost $5 per coin, with values all within a $5 range of each other, I probably would just go with the average cost too. I'm not that anal .