3 TC for a 4-use item. These uses are based somewhat on RNG: There's a 24% chance for these charges to do nothing upon use for a basic PDA. If the target PDA has any special cartridges, this chance is increased:
If the PDA has a syndi uplink, it will always fail. This is the reason for the RNG -- traitors having their PDAs get blown really sucks. However, if the RNG is removed then the carts can be used to determine which PDA belongs to a traitor (the one that gives an error). But because of this, you can easily COMPLETELY waste your investment because they all failed. The cart can also be rendered useless by the target turning off his PDA, or by telecomms being destroyed.
Let's look at other bombs: The detomatix explosion is a -1, -1, 2, 3, which is very weak. C4 is 2tc for a -1, -1, 4, 4 explosion, which is bigger but still pretty mild. A minibomb is 3tc (same price!) for a menacing 1,2,4,flame_range = 2 The syndicate bomb is only 2tc more for a 2,5,11, flame_range = 11 blast of mass destruction (if you don't know what these numbers mean, these are explosion ranges (devastation, heavy, light) measured in tiles).
If you want to compare to a non-bomb option, the revolver is a 6tc 7-use item that can crit someone in 2 uses and can also be refilled if you have the opportunity(!).
Personally, I think there are too many issues with this thing to bother trying keeping it. Even if the explosion was made more worthwhile and the RNG issue fixed somehow, I don't think "oops you got blown up from across the map, probably at random, probably at roundstart so at least now you know it's a traitor round!!" is a very interesting mechanic.