The base econ is the max econ for that defensive configuration

Base Econ 34
Plasma 10/Ion 10
100 to 400 fighters
1 HC per 100 fighters

Base Econ 41
ion 10/Ion 10/Photon 10
200 to 600 fighters
1 HC per 100 fighters

Base Econ 103
Ion 10/Photon 10/Disruptor 10
1000 to 2000 fighters
1 HC per 100 fighters (max 20)

Base Econ 109 Only here for informational purposes
Ion 10/Photon 10/Disruptor 10
1500 to 2500 fighters
1 HC per 100 fighters (max 20)

Base Econ 122
Photon 10/Disruptor 15
2000 to 3000 fighters
20 HC

Base Econ 138
Photon 10/Disruptor 20
3000 to 4000 fighters
20 HC

Base Econ 188
Disruptor 20/P shield 5/P ring 5
4000 to 8000 fighters
20 HC

Base Econ 266
Disruptor 20/P shield 10/P ring 10
2 DNs

Base Econ 325
Disruptor 20/P shield 15/P ring 20
2 DNs

Base Econ 376
Disruptor 20/P shield 20/P ring 25
2 DNs

My opinion differs from many about that Issue and I have resons why. Maybe I can debunk some of them issues. Like the reson why PPL should downgrade from ION turrets seeing that the Ion turrets, From Testing on Delta Proved that the Ion turrets if left will add a 1/4th damage cross over to defences like Prings and Disruptors. I won't downgrade a good thing.
Photon are better as far as damage and shield/defenceive armor. But they don't have the cross over shield to ship rating of 1/2. Disruptors destabalize ship shields but Ions cross over, with both that makes a BIG diffrence in calculations in defence.
Deflector shields are the First line of defence in a attack It has also been made clear to attackers that if the shields are not down you can't hit the Turrets. The Deflector shields are calculated first and added to the shield rating of the turrets. If you have shielded turrets and still have plasma turrets and less on your base, get rid of the lesser turrets. they mess up the defencive capabilitiers and weaken Better turrets shield/armor ratings.

Trade Route Attacked Copy Savebox 01-09-2008 18:30:45
Your Trade Route from TNT Railways ([DEAD!] Uncle Fester) to Ayte ([JLA] Captain America) has been attacked by [~o] Draconian; the trade ships were plundered and the trade route was cancelled.

This is another reson defences are Importaint. A weak player on the other side can pillage your route making a killing in Creds. Because this guy ([JLA] Captain America) had crap for defences and did not upgrade or listen to my suggestions I am out 2400 creds. Get with the Program and build your defences first worry about attacking later After you have the stability of Better base quality. More PPL will also like to trade with you then knowing you are protecting your Investments.