So I know that understanding the mechanics of the game, especially the math (thanks theenginescannaetakeit and Jupiter Broadcasting) can be huge for succeeding in the game. So I'm seeking help understanding the following.

First off, while searching the Exchange I came across two consoles for Mk X Uncommon Sensor Probes. Some (the cheaper ones) were +15 and others of the same description (but higher priced naturally) were +30. I've seen slight variations in the equipment being purchased from K7 and Omega Fleet but this seemed out of whack. Where are people getting these?

Second, my consoles I'm equipping are not showing the advertised effect when I look at my ship stats under General, Defense, Attack, Movement.

Examples:
Montanium Alloy Mk VIII (Rare), +28% kinetic dmg resistance. Yields +21.4% resistance when equipped

Tetraburnium Hull Armor Mk IX (Uncom), 21% varius dmg resistance, Yields 17% resistance

RCS Accelerator Mk X (Uncom), 22% Flight turn speed, turn speed shows 3.0 deg / sec equipped or not, ie, no effect on ship stats.

Someone please enlighten me.

Easy enough to answer your questions m'friend...

Those Crazy Consoles:

What your actually seeing is consoles that were originally realeased in the early stages of the game. After a few weeks though they decided that they were drastically overpowered and thus lowered all of the new ones. However, players still had the ones they earned and so sell them now for ludicrous amounts of dough.

Console Conundrum:

Any of your defensive consoles have what they call "Deminishing Returns"... meaning that the higher the number, the more you lose. Kind of like a 'defense tax'. I suppose it's to prevent players from stacking consoles and powers to the degree that they are completely invulnerable.
About your turn rate, simple math really... there is no improvement visible due to the fact that 22% of 3... isn't quite +1. So your not getting much help there, but I bet you will still notice a diff IN actual play if you try it out. You just won't see a number diff. Get it?

Resistance consoles and powers don't have diminishing returns, they're simply labeled poorly. They should say "+x% damage durability" instead of "damage resistance".

Using that Tetraburnium 9 as an example, it means it takes 21% more damage to kill you, which is why it gives you 17% resists. Instead of 1000 blowing you up, it'll be 1210, it just does that by reducing the damage you take instead of increasing your hull points. So, what number reduces 1210 to 1000? 17.35% It's not a coincidence.

Consider the alternative. If that console actually gave you a straight 21% damage resistance, then slotting four of them gives you 84% damage resistance, meaning instead of 1000 damage killing you it's 6,250. It's pretty obvious why it doesn't work that way. Each console would be exponentially stronger than the one before it, and with an engineering team going you would be literally immortal (100% damage resist).

Nothing in the game has diminishing returns except ground crowd control.

Make sure you're in the right zone to see the results. You won't see proper ship stats on the ground. You have to be in space, and at speed. I think to see proper turning you have to be at or above 25% Impulse. The way I've tested RCS in the past... I beam up from the starbase, set my Impulse throttle to about half-way. I watch my speed until I've stopped accelerating. Then I open my User screen, click over to movement and add/subtract the RCS and note the differences.

Also, I know when I have no RCS and take my engine out my Turn Rate goes to 3.0 degrees. I think this is the base turn rate (of your maneuvering thrusters, I guess?). When you put in your engine you'll get your ship's turn rate. Then if your Engine has a Turn bonus (like mine has +6.4), it adds. I haven't been able to figure out the turn rate maths, since even when in the RCS don't seem to give what's written on them (again it's probably just poorly written).

And don't forget, there are skills that improve your turn rate (Starship Combat Maneuvers for example) - though these are tiny amounts.

Thank you all of you for answering my math questions with math answers. I was a bit worried I'd get a lot of opinions. Indeed, I was looking at my stats while in Starbase while swapping equipment. While flying around I did see my stats change after 25% throttle. A 180 deg turn was reduced by 2 seconds. The stats aren't very intuitive but they make sense now.