The more expensive a trap is, the higher its accurancy penalty is.

Is this intended? If yes, why?

Hello, Madscientist.  They are less accurate because a player with very high Mechanics skill counteracts the penalty.  A player with high Mechanics skill and a low level trap will crit very often.  A higher level trap will not crit as often.  A player with low mechanics skill is not going to be able to make up that difference and therefore is not as effective with the traps.  

 

This mechanic encourages the player to put down traps with characters that are able to use them more effectively.  If a player wants to put down a high level trap with a character that doesn't have a high enough Mechanics skill they can, but it's not going to work nearly as well.  Thanks!

Is there a way to see what accurancy the trap will have, when char x with machanic skill y wants to use it? (except placing the trap and looking at the combat log when it hits the enemy.)

When I put the mouse over a hostile spell in the hotbar, the tooltip shows the accurency and targeted defence.

This is not the case for traps or scrolls.

 

So the attack roll for the trap in the right picture used by a char with 0 mechanic skill is: X = (-40) - (target defection) + 1d100

The accurancy for a scroll is: X = (base spell accurancy) - (enemy defense) + 1d100

 

It would be nice to have, if the tooltip for hostile items shows the accurancy in the same way as it does for hostile spells.

Hello again.  I will pass this suggestion along to the proper team.  Thanks for your support!