I bought the gantries, and upgrades.
Launching and anchoring the gantry,taking 3 seconds. Placed the upgrades in and hit the upgrade, probably taking another 2 seconds.
Upgrading the gantry is quick; taking 30 seconds to become a full customs office.
Note about ninja customs office placement : in about 5 seconds, you have decloaked, launched and put upgrades in, and clicked the upgrade button. Your customs office gantry has far more HP than can be bashed in 30 seconds in highsec, and even then you can place it 100k away; enough to be on grid, not enough to warp to.
So, for the effort of keeping an eye unexplained BS in your systems (or fleets of other afk bashing ships), you might get your customs offices placed.
For the attacking corp to return the favour, it will cost them 24 hours to apply the wardec, finish a timer that you have specified; come back when the timer expires, and is favorable to you, some 24-48 hours later.
The default player corp customs office is 10% player, 10% NPC (on untrained pilot), making a total effective tax rate 20%. Many corporations will start out with the default.
Customs code expertise does not appear subject to diminishing returns. My pilot currently has this skill at 3 and learning more, and is reducing tax by 3%. My reading suggested this, but it is better to see the numbers in game.
Even with customs code expertise 3; I have no reduction in interbus tax rates from 17%. The same as my Singularity pilot without any customs This surprised me.
Given the prevalence of 0.1 isk undercutting nature of many Eve players, I expect there to be many 11.9% taxed player corp customs offices, especially if any cartel or 'protection' groups form. 11.9% + max skilled customs code expertise makes for 16.9% effective tax; cheaper than NPC, but only just.
There will be a limit to the number of groups capable of bashing out regions of customs offices.
- customs office gantries are limited by concord LP.
- DPS to quickly kill a customs office. 500dps to break tank; 700dps to get there eventually; 2000 dps to do so in a several hours.
- ISK to buy gantries and upgrades; This will cost very roughly 1B/system. Some of us are comfortable buying a system or 2 of upgrades; Only a few have the ISK for buying a region of customs offices;
Whether it the 7 Marauder pilot years or the 2,500 billion ISK (using planet numbers and DPS from greedy goblin's post) ; this is multi 'alliance' level task to take on all customs offices.
Much less of an issue to bash out 'high value' customs offices in preferred regions.