The amount of minerals and materials you will need to execute one run of a blueprint depends on (1.) your production efficiency level - which should be at level 5 before you attempt to compete in the marketplace (2.) the efficiency of the installation - as far as I know all high-sec stations have an installation efficiency of 1 whereas POS assembly arrays can have efficiencies greater than 1 meaning they are relatively inefficient. (Advanced Large, Medium & Small Ship Assembly Arrays have a Base Material Multiplier of 1.1 and Rapid Equipment Assembly Arrays have a Base Material Multiplier of 1.2 (3.) the Material Level of the blueprint. By researching the blueprints Material Efficiency you can reduce the amount of materials needed - sometimes this will make enough of a difference in a competitive market to give you an edge.
HOW MUCH OF A DIFFERENCE DOES RESEARCH ALLOW FOR? As the following examples show, its not always the same, and it isn't necessarily very much.
Example One.At PE 5 an unresearched Scorch Bomb BPO (ME 0) requires 11081 Isogen, 358 Megacyte, 59649 Mexallon, 2333 Nocxium, 616637 Pyerite, 1503325 Tritanium, 1437 Zydrine. Once researched up to ME 50 (Waste Factor 0.2%) it requires 11080 Isogen (99.99%), 357 Megacyte (99.72%), 59648 Mexallon (99.99%), 2332 Nocxium (99.95%), 616627 Pyerite (99.99%), 1502345 Tritanium (99.93%), 1436 Zydrine (99.93%). The difference is so marginal that ME research does not significantly effect the amount of minerals needed to execute one run.
Example Two. At PE 5 an unresearched Ultraviolet L BPO requires 2 Isogen, 19 Megacyte, 3 Nocxium, 103 Pyerite and 4 Zydrine. After being researched up to ME 21 (Waste Factor 0.5%) it required 2 Isogen (100%), 17 Megacyte (89.47%), 3 Nocxium (100%), 94 Pyerite (91.26%) and 4 Zydrine (100%). Despite having a lower ME of 21 vs 50 and a correspondingly higher Waste Factor of 0.5 vs 0.2 the Ultraviolet L benefited more from ME research than the Scorch Bomb. Therefore you can not expect when researching a a BPO that based on previous results your researched input requirements will change in the same ways - especially for very different types of items.
So now for the million ISK question and the point of this post. If you can't predict in advance what the benefit of research will be - how can you nonetheless know what the benefit of research will be? This is especially important when deciding what to manufacture in the first place...you have to know what the actual input costs will be in order to compare any two items. The solution is very simple - search the contracts window for researched BPOs, view the contract and then correlate the ME# with the mineral or material requirements.
I have a very large spreadsheet that compares the market value with the mineral value of hundreds of different items so that I can determine the margin of return on building any of these items. Ideally you want to build items with the highest margins, few competitors in your trade center and reasonable volumes.
A brief note about selling - train Accounting to level 5 - this will reduce the transaction tax YOU pay when SELLING an item. (caps because in the real world tax is paid by the purchaser when buying.) Also, when selling items on the market to existing buy orders use the "simple view" window because you are taxed but not subject to a brokers fee. When selling onto a Market at prices above the highest buy order you must use the "advanced view." This will subject you to a brokers fee that depends on the skill Brokers Relations and on your Faction, Corporate and Personal Standings. With BR 0 and standings of 0 you are assessed a 1% Brokers fee. Training Brokers Relations to level 5 reduces this fee to 0.75%. With high standings I've read this fee can be further reduced to 0.3%.