Compare prices in smart shelf?

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Current value and retail price are only somewhat useful information to have for items you already own (insurance purposes aside). On the other hand, they become very useful and very interesting when one is significantly greater or lower than the other, and/or either is greater or lower than purchase price.

Sorting by price fields isn't all that helpful with a large library/shelves and I can't find a way to compare prices via smart shelves. My current workflow is to select fields for export, export to csv, import in Excel, strip currency symbols, set up formulae and finally sort. This is more tedious than it needs to be.

Is there a way to do this from within DL that I've missed? If there is, please advise. If not please consider the following to be feature requests:

1) Smart shelf conditions for price fields being greater/lower/equal to other price fields would really hit the spot.

2) Greater/less/equal to user-set absolute values is also somewhat useful (i.e., if current retail price and current value of a DVD are both less than $10, you've got a coaster).

3) A workaround for not having calculations in smart field conditions could be made if a smart shelf condition for an item being on or off a shelf existed (i.e. Shelf A is made of items with low purchase price. Shelf B is made of items with high current value. Shelf C is smart, with conditions that items be on A and B). Compare this to iTunes smart playlist condition of Playlist is/is not. I can think of several other ways this last one would be useful as well.

Thanks in advance.