For the most part BPC are dirt cheap to make, some just take time (which could be quantified into a value as well).
The biggest pricing factors that come to mind are:
- Runs on the copy
- Price of BPO copied (Not everyone can buy a Titan BPO and start making copies)
- ^ related to that one, but generally how long it takes to get the ME/TE of the BPC if it were a BPO
- Meaning a 0/0 titan BPO anyone can throw in, but first researching the BPO and then making copies takes a bigger investment of isk and time
- How many of the same ME/TE on the market
- Convenience: Is it worth traveling to jita to buy them and then risk losing them getting hauled back to my building system in LS/NS? OR do I pay a higher premium because the BPC back is being sold 2 jumps away from my manufacturing plant
As far as I know there is no formula, its much like the market where it trends up/down based off people throwing up more on contract and slowly .01 isking each other in price. Much like the market you do from time to time get that person that just wants to liquidate and puts things up for dirt cheap, which skews the price of the market for a bit until those are all bought up.
Also take into account the people selling them on the Sales section of the Forum. That doesn’t translate as much into the in game prices because not everyone watches the Sales ads out of game.
I believe some of the long standing BPC pack sellers have a regular customer base that don’t shop around and always just come to them, a time built reputation goes a long way here as well.
Its a game of supply and demand and convenience.
I claim to be no expert, and I generally only deal with the BPO market and not BPC, this is what I’ve observed.