Never give a virus a missile launcher...
(or anyone who doesn't have the budget of an over-bloated military)
20 Sandcaster Barrels - Cr 10,000 (200 ea)
12 Basic Missiles - Cr 15,000 (1250 ea)
12 Smart Missiles - Cr 30,000 (2500 ea)
12 Nuclear Missiles - Cr 45,000 (3750 ea) *And just how did you acquire nukes? nudge nudge...
I didn't see a cost for Pebble Barrels for the Sandcaster, but it's reasonable to guess it's the same cost.
If you're going to use Missiles, and you don't have supergunner, go for the Smart Missiles, they cost twice as much, but they keep attacking until they hit or get destroyed. That alone can save your thrusters on a bad day.
Any weapon that has you throwing away money gets expensive real quick, but if you are a relatively secure trader, the threat is worth more than actually using them. Of course, stupid adventurers get in shooting matches way too much, it's worth the initial investment to get weapons that don't cost Cr to shoot, and have infinite ammo. (As long as you have power, of course, no power, you've lost the fight anyhow...)