There are a number of B-Type and C-Type modules that don’t provide reasonable alternatives to their A-Type counterparts due to exceedingly low spawn/drop rates - frequently as low as ~1/10th their A-Type counterparts, and sometimes even lower.
Because of their super low spawn rate, many of these items will trade upwards near their A and X-type counterparts, despite being strictly inferior. This frequently creates a big price jump from t2/faction modules to A-Type modules, with no valid in-between.
The majority are frigate-sized items, and it’s particularly painful not to have a reasonable intermediate price point for frigate mods - you either fit your frigate T2 or you have to jump up to paying hundreds of millions to fit out a shiny frigate, with no valid in-between option.
The average daily market volume gives us a glimpse of the drop rate of deadspace items. Take for example Centii A-Type Small Remote Armor Repairer, which has an average daily trade volume in Jita of 69 units (nice), and a current sell price of 25m. Centii C-Type Small Remote Armor Repairer has an average daily trade volume of only 4.73 units, and costs 19m.
Thus, the super low drop rate of C-Type small RR is preventing it from providing a valid in-between option for small RRs. You can either spend 4.5m for 3 T2 RRs, or you can jump all the way up to spending 75m for your set of A-Type RRs.
A healthy price point for C-Type small RRs might look like something like 5 mil per, so you can get a set for 15m, and B-Types might be ~10 mil per for 30m total. That way, there would be logical price point scaling like there is for items where the drop rate is more even.
This drop rate issue also means that even a modest-size alliance cannot use the affected B & C-Type modules on doctrine fits, as their demand would immediately buy out the entire market, and drive them up to ridiculous prices.
Multispec coatings are the main example of this: Coreli A-Type Multispectrum Coating has a daily average trade volume in Jita of ~157 units, but B-Type is only ~7 units, and C-Type is only ~9 units. The B & C-Types spawn so rarely that no reasonably sized alliance could put them on a doctrine fit regardless of price. There simply aren’t enough on the market!
Here’s a list of these super low drop rate B/C-Type items. I think it’s relatively exhaustive, but folks can feel free to reply with any additional problematic items they find.
Centii B & C-Type Multispectrum Coating
Coreli B & C-Type Multispectrum Coating
Corpii B & C-Type Multispectrum Coating
Coreli B & C-Type 1MN Afterburner
Gistii B & C-Type 1MN Afterburner
Coreli B & C-Type 5MN Microwarpdrive
Gistii B & C-Type 5MN Microwarpdrive
Gistii B & C-Type Small Shield Booster
Pithi B & C-Type Small Shield Booster
Centii B & C-Type Small Armor Repairer
Coreli B & C-Type Small Armor Repairer
Corpii B & C-Type Small Armor Repairer
Gistii B & C-Type Small Remote Shield Booster
Pithi B & C-Type Small Remote Shield Booster
Centii B & C-Type Small Remote Armor Repairer
Coreli B & C-Type Small Remote Armor Repairer
Corpii B & C-Type Small Energy Neutralizer
Corpii B & C-Type Small Energy Nosferatu
Corpum B-Type Medium Armor Repairer (C-Type looks ok)
Pithum B-Type Medium Shield Booster (C-Type looks great)
Corpum B-Type Medium Energy Neutralizer (C-Type looks ok)
Corpum B-Type Medium Energy Nosferatu (C-Type looks ok)
Corpus A, B, & C-Type Heavy Energy Neutralizer (vs X-Type)
Corpus A, B & C-Type Heavy Energy Nosferatu (vs X-Type)
Gist A, B & C-Type EM Shield Hardener (vs X-Type)
Pith A, B & C-Type EM Shield Hardener (vs X-Type)
(the other flavors of shield Hardeners too, but EM is obviously the most common by far)
[Shield amplifiers are OK]
Armor Hardeners are mostly OK despite relatively low drops, presumably because there are 3 races and 4 tiers of each.
Large Armor Reps and Large and X-Large shield boosters are arguable. Their drop rate of A, B, and C-Types tends to be about 1/2 that of the X-Types, compared to the 1/10 ratio that plagues most of the mods listed above.
As to how to fix this issue, I’ll leave that to CCP! Deadspace sites represent a very, very old gameplay feature that could use some serious rebalancing, but a more targeted adjustment of the most problematic mods above would certainly be much, much easier than some kind of sweeping overhaul.
P.S. I notice the Ideas & Discussion section of forums disappeared, so I wasn’t sure where to put this post. Feel free to move it!