Factors That Influence A Coins Value And Collectabillaty

You are so right, just too many aspects to consider, however I do believe that in order to make sound decisions every investor or collector out there has his/her own motivators to consider when evaluating buying of a new coin.
It is in the end as simple or complex as one would make it.

I agree with weavus - I go for the coins I need, not for the coins that will raise in value. Granted, knowing this stuff helps understand why certain coins are soo expensive in comparision to their counterparts. Me personally, I pay attention to the mintage amount - less minted it usually going to be key.

Mintage definitely plays a part, but it's more the "popular" series that are affected by price.
Lincolns, mercs, morgans... all are overpriced in my opinion, at least going by the mintage. But the demand is high because everyone is trying to put together sets of those. The S VDB, 16-D Merc, 93-S/94-P Morgans are not rare by any means, but with demand comes a higher price.

Half Cents, most Seateds, $3 Gold... are underpriced according to the mintage. But not many people go back that far (as far as sets go) so the price stay relatively low.

But a "low mintage" coin of a popular series will have an inflated price for that reason.

And what influence collect-ability would be if someone can put a set together at a reasonable price. So where there are Proof-Only issues, dates less than 100 known are not going to be very collectible because people want that album hole filled. Otherwise people with their 7070 just need one type, and often is the most common of that type which will raise the price for that coin while the others are neglected.

At least that's my take

I like to go after the more rare coins that I feel are underpriced.
Nearly all the "popular" sets have doubled in the past 10 years across the board... what has pretty much stayed the same is what I mentioned earlier, Seated coins... or most stuff in the quarterly section of the greysheet.