"Bronze items give you about 10 EC, while silver give 20 EC for each item." I don't think it's that much, but you are at least somewhat-right.
I went through on a calculator and added up the number of excess items (EN+ items and Muscle Cylinders), and it was less than the amount of extra EC. Therefore, some items might be worth 2-5, but not as much as 10 or 20. --- Official Anthony of the Shin Megami Tensei IV Board ^the perplexity of an absurd delusion*