It's all about crafting.
Gatherers always talk about how easy it is to farm mats from planets and what areas to get the most nodes.
Really? You expect me to spend all my game time wandering old planets hacking nodes? I've got better things to do with my time.
I can buy the gear you spent hours gathering in 30 seconds from the GTN. Set my companions to craft and logoff to get some sleep. In the morning I'll sell that gear for 5-10 times what I paid you in materials, my time spent is maybe 30mins tops. And I neverhad to leave my ship to do it, I just ran warzones and flashpoints making additional money while credits rolled in.
People brag they made 4 million gathering but never tell you how many mind numbing hours they wandered old planets to get that. If I put in 30 mins a night, 5 days a week; I can make about a million a week on average. And I don't have to "invest millions RE'ing schematics". I'm selling blue mid level gear that cost 350 for the schematic, and about 4 green items reverse engineered for the blue schematic.
My main play is PvP. The millions I make a month is a 10-30min a day side job that runs while I do fun things.
You're doing it wrong.
There are much, much better ways to gather materials than "wandering for hours". And while you make your million a week crafting I can make that plus many more millions gathering materials for GTN sales AND crafting items.
What it boils down to is willingness. Money isn't going to just rain down on you without effort and the more effort you are willing to put in the more you will earn.
Since your main play is PvP you don't have much of a need for credits unless you want to buy CM items from the GTN to customize your toon as the more important gear is obtained through ranked comms.
The key, as usual, is doing research. You have to know where to farm materials, which materials are worth farming...without that knowledge you are gambling that your time is being well spent.