I'll get straight to the point:

Does the lower tier skills have a lesser value than the more specialized (and more expensive) higher tier skills?

For example:

Lets say i want a bridge officer with Tachyon beam. The skills i would have to train are as follows:

Tier 1: Starship Operations Training (9 skill points costs 900 points for +18)
Tier 2: Starship Deflectors (3 skill points costs 600 points for +18)
Tier 3: Starship Deflector Dish (2 skill points costs 600 points for +18)

Now i just ad them together: 18+18+18=72 and this would be my final score for my Tachyon beam.

I've heard a rumor that the +18 from Tier 1 will not be as beneficial for me as the +18 from Tier 2 which again won't be as benficial as the +18 on Tier 3.

I do know that this setup for my tachyon beam is by no means playable but it will give me some pointers as to how to distribute my ground skills, because i do not maximize my ground skills.

I'm certain that you guys will be able to help me