I've played around with the numbers and values for average warriors some and have come up with the following:
The basic warrior profile for SBG costs 5 points and has Fight skill 3, Str 3, Def 3, A 1, W1, C3 and move of 6, basic hand weapon.
Analysis after the break----
To deviate from these numbers-
Fight skill- costs 1/2 point value per full point of fight skill added.
Strength- add or subtract 1 point for each point of str changed
Defense- costs a point to add a point.
Courage- costs 1/2 point value for model to add full point of courage.
Regular bows- cost a point
Elf bows cost 2 points
Losing the option to take a shield deducts 1/2 a point
Adding a shield costs a full point.
having a shooting skill < 4 costs 1/2 point, while adding skill above 4 deducts 1/2 a point
Given this system, there are some relative bargains out there because models are often undervalued by a half point. Knowing this system then, allows you to select models that the most cost effective for your army.
E.g compare a standard harad warrior vs. a warrior of rohan. They have the EXACT SAME stats. So why does a warrior of rohan cost 6 point and the harad cost only 5? The answer if because the rohan warrior can take a shield while the harad can't. If you ask me, so what, but the game designers thought it was important. So, Harad should crush Rohan because they will have on average 20% more guys in their army compared Rohan.
having said that, some of the most cost efficient model work out to be Morannon orcs, elves and harad.