I don't think many people will give up their prized LP items simply because of to many people start selling that item because it's 'good' there will be an over supply of that item and prices will plummet thus it's no longer good ;-)
Just a hint, you can make between 200-300 mil/hour in LP alone from FW missions (for Gallente at least, not sure about the other factions) depending on player interference) Study the LP store, grab that calculator, see how you can maximise LP per hour and find out what gives most ISK/LP.
You have to remember it's not only ISK/LP that counts but also how long it takes you to get that LP. If you get 6000isk/lp but it takes you say 6 hours to get 300k LP, and another faction etc gives 3000 isk/lp but it only takes 3 hour to get that 300k LP they are both equal.
Always take the conversion cost of LP to ISK into account when calculating isk/lp. If you can trade in say 300k LP, sell those items for 1.5 bil, but converting them costs 400 mil (in tags, items, conversion price etc) your profit is 1.1 bil/300k = around 3.6k isk/lp, NOT!!! 1.5 bil/300k = 5k isk/lp
Merged as proposed
For all intents and purposes, this question the same as http://skilltrainingcomplete.com/questions/3744/how-do-i-maximise-my-lp. Propose they be merged.