well at the moment people in eve don't really own planets, they own the system that the planets are in.

the way we make isk is by building factories on these planets and this can make up to a billion a month depending on how active you are.

to place these factories in 0,0 you need to own the system, or if no one owns it then you can put down your factories.

also to make things more complicated you have to export your stuff you made via a customer office, and players can own these and set the tax rates so its best to own these. ( these can only be owned in 0,0 and low sec for the moment)

I'm guessing 20bil or more, it's a micro managing nightmare that few take pleasure in..

EVE currency =/= Dust currency.

A planet yield depends mostly on sec status hence 0.0 is best producing basic raw materials and high sec is best suited for producing limited quantity items where taxes don't margin your profits.

So we take an example of making 5x mechanical parts and 5x consumer electronics per cycle:

Noble metals9000
Heavy metals6000
Base metals6000
Non cs crystals3000
Noble gas3000
Ionic solutions3000
aquenous liquids3000

Precious metals60
Toxic metals40
oxygen20
reactive metals40
electrolytes20
water20
chiral structures20

Mechanical parts5
Consumer electronics5

These will give you 3x robotics per cycle in the end.
Time per tier is:
T2 T3 T4
time min/ units280min/13340060min/4060min/1060min/3

That makes it some 3-4 hours to get your first patch of 3 robotics no this planet example I'm using which is an actual planet that I slapped in exel.
Naturally having materials ready reduces the initial start up time.

So with this we can estimate how much your planet will make you in the market:
With the simple assumption of one robotic per hour and the price from jitonomic which is around 50 000 isk per unit:

So 50 000 isk x 30*24 = 36 mil per month assuming you would have only one factory making robotics but since any serious with PI has several factory planets you can easily get 20 of those factories with the limit being how much you care to haul materials and baby sit your planet yields.
You can also drop the extracting and buy stuff from the market but often (as in most MMO's) the actual end product is cheaper then materials you (bought and) made it from which obviously happens because:
YOU IMBECILES DON'T KNOW HOW TO COUNT AND THINK THAT BECAUSE I EXTRACTED / MINED IT, IT'S FREE OF CHARGE.

and next time ask something simpler ?

uhh....

Basically what i've been told is planets can dump out 100-500mil isk a month, so basically one planet being defended could be used to hold up a entire team wasting tanks and all that stuff.

Average pay of an eve player is about 4.5 million isk an hour give or take. There are plenty of smarter players who can break that point though.

Market prices IRL works roughly like this: Sale price = projected profits over 20 years.

There you go, back to work for me..

Edit: The work for EVE/Dust is to figure out what an appropriate conversion for the IRL 20 years is. 3 months? Half a year?

could be interesting to see how much ISK you need to spend to hire a 16 man team (max players at the moment) cause if you expect lets say after the match each merc gets around 100.000ISK multiplied with 16 makes 1.6 million ISK just to control 1 facility. And i dont think you control all of them by just 1 skirmish match. i heard 1 planet has around 12 skirmish maps so 1.6 million multiplied with 12= 19.2 million ISK. And thats not counting in the costs for defending. I think better players/corps will demand a higher payout to defend or attack.