It is common, during reports of upcoming expansions (now 'patches') that items (newly introduced or buffed) will lead to a inflated market cost. What happens, as in real life, when something is hot, people gobble up inventory and sit on them until such a time as they reach their maximum value and high demand. I remember back when rails got buffed, people invested heavily and were rewarded when people started fitting rails to their ships. They made a lot of ISK. The keen-eyed observer can see those market trends, speculate on market performance and sell when demand and price are high. There is an old adage, "You have to speculate to accumulate".
Edit: I hate retractions, but such is the activity when I give misinformation. Pointed out by Zhilia Mann, I used the wrong graphs. I have corrected my post to show 'capital' cargohold optimization rigs. Coincidentally, it shows a similar bubble as the large cargohold optimization rigs...
This brings me to Kronos. I imagine there are a bunch of people who went out on a limb and bought up or manufactured cargo rigs in preparation for a market run on them when freighters are modified for the Kronos release. When first mentioned in the Dev Blogs, freighters were getting a nerf to their cargohold size and getting equipped with rig slots.
After deliberation, they decided to change them to low slots. While this is actually a lot better than rigs (you would have to destroy them to fit your logistical needs should they change), so it would be costly. With low slots, you can customize your freighter as you see fit. The downside is, anyone who took the risk with rigs is now probably scrambling to dump them.
I can show you this with the use of EVE-Markets.net's graphs.
Looking at Capital Cargohold Optimization I's 90day history, you will see a large bubble and a steady decline. That coincides with the initial announcement of the freighter/rig modification. Looking at the median average, there was (if my math is correct) about a 48% increase.
People who own freighters would probably try to fit T2 CCO's to get the most out of the rig slots. That one, as shown below is in the same neighborhood. We are looking at a median average rise of about 43%.
Speculation can be highly advantages or financially devastating.
Speculate with caution and as always, fly safe-ish.