If you really play pinball then a grail pin should be more then just the theme. They way each designer put a table together makes a massive difference on the playing style, fast and flowy, vs stop and go, mode based vs overall progression, wide body, standard body. There is only one table in my collection that I would consider grail and it's not mine it my wife's Addams family. For her its a bit more simpler as this is a table she grew up with in a share house during her university years and to her it just represents pinball. However she is not going to get much more into the hobby then knowing she enjoys playing the occasional game and has a fondness for the Adams family. Any other table is up for grabs either to sell or buy in my books as almost every table out there is replaceable. If she chose to sell it that would be up to her but it wouldn't happen unless a real family emergency warranted it, even then all my other pins would go before as they have no sentimental value. Once you been been in the hobby a while you realize that all pins are just a commodity, and all can be replaced. The term grail pin might apply to a collector who has spent 10 years and 30k tracking down a kingkong for example because hey you ain't going to get another, but really almost any game is replaceable expect for a very select few that are truly rare. I don't buy into Stern trying to create rareness via le and super le. When you have the exact same gameplay available in unlimited quantity in premium, then the game really isn't that rare.
That being said anyone selling a game should remember just what it will take to get a replacement should they choose to. Someone offering you silly money for your pin might seem like an easy win, until you have to go out and try and replace it and see that the market has moved beyound your expectations. This is really true of high end restored pins. It takes a bucket load of money to get tables back up to true collector quality and beyound. Even at the ridiculous price some sell for they are still below replacement.
Personally I've stopped buying and selling pins as I'm happy with the collection I've got and find it much more enjoyable to play new games on location. Would be a very diffrent matter if I didn't have good locations near by. It's a lot of hassle moving pins and changing the collection up frequently, and the truth is, every game gets old after a while so there is not much benifit in swapping out.
Build your collection around games based on your preferred style and you will find you will play them much more then if you base them in theme. If you play your games more often you will enjoy the hobby a lot more gaurenteed.
I have no problem per say with new tables being priced at 9k as I have spent that on machines before. However I do believe that there is a lot higher potential for buyers remorse on nib at this price. With older games you know what you getting as far as gameplay rules etc. if you do your homework and really check a table over before dropping 9K you will most likely be happy with your purchase and get 1000 of hours of entirtainment. I find it hard to believe that people are going to have the opportunity with newer games to spend the time on them to really feel 100% sure this is a table that they would be happy with, and is a 100% keeper. personally to feel that comfortable would take a 50 hours or play on a table, many many months. We all have themes we believe can provide the perfect pinball experience, but pinball needs to be played not imagined. Sometimes our dreams and reality are very different. The truth of this argument is that the people going in on say Dialled in at 9k or Batman 66 at 10-15k are doing so because they are in a financial position, where they can afford to take a hit on the game if it turns out not to be all they hoped. 9k is not the high end price of pinball it's just a lot of money to be throwing at games you have had very little hands on experience with.