Not easy to answer in one sitting but I will make a start.

You have to bear in mind that the book shows value codes, which cover a price range, and those ranges are relatively wide in percentage terms.
In our database, we store finite values (the basis of which I discuss below) and so many changes do not necessarily result in a value code change, but could increase the chance of a change next time round.
We feel it is more important for the higher value chips to be meaningfully priced. So even though there may be little or no current price data to go on, commonsense dictates that there are no longer any chips priced at Z8 or Z9. We did actually take a thorough look at every Z chip and adjusted accordingly.

On the other hand, when you look at the lower values, say A-H, there are, and always have been, wide swings in price in the marketplace on a day to day basis, so to adjust any of those on the basis of the last seen sales prices is rather asinine.
Most customers, yourself included based on what you buy from me alone, are not too concerned if the chip is costing you full book by the time you have it shipped when you are talking $5, $10, $20 a time. You may find the same chip 30% cheaper somewhere else but that doesnt concern you. However, if I offered a chip you needed for $500 and you could buy it 30% cheaper elsewhere I am sure you would do so. The exception to our valuing at the lower end (and in fact for any value code) is any significant quantity find of a chip which is going to have a long term value implication, in which case we will adjust the value to where it will likely fall after the chips have entered the market (because anyone who continues to pay the 'full' price is overpaying market value).

That leaves the 'middle' values - ie $50 - $800. This is where we concentrate on trends of actual sales known, and we look at the factors that have affected their prices. In some cases, this will lead to an adjustment in 'like' chips, but Ive not seen any correlation in the type of examples you quoted (buildings, dovetails, pies) that justifies adjusting the prices of similar style chips.
We do of course refer to ebay prices, and you might be surprised to know that while many chips do sell for only 1/2 low book, there have been a considerable number of sales in the past year that have exceeded high book (I guess those were the ones you were outbid on ). Also, while many chips sell lower on ebay as I have indicated, I have offered and sold many of those same chips on my website or in sales at 'full price' during the same time frame so where that has happened no adjustment would be made.

You mention LE's - bear in mind the vast majority are valued at $5-$9 and the vast majority are still redeemable. So even though their popularity may have decreased it doesnt change the price band. After all, what is changing here is merely the proportion above face that people are willing to pay. If the Palms for example issues 1,500 of a $5 and only a few hundred are bought by collectors/dealers, then within a pretty short space of time the rest will end up going into play on the tables. Not much longer and they are all beat up. Nearly all LE collectors want uncirculated chips. The less that are bought from the casino, and the more that are turned in by dealers and becoming 'used', makes the chips scarcer, so they hold their value even with less demand. If there is a future upturn and more new collectors want LEs, then the shorter run ones are more than likely to increase in value.

Coming back to the 'trend' question, I guess if you were to compare the stats at the back of the book where it shows the number of chips per value code, then you would be able to see downward and upward trends edition on edition, yes.