I am only making 230 silver an hour doing Centaurus herd. I am a witch I have 269 AP and one shot everything. I have heard people get 1 billion silver, I don't even know how that is possible!

You can get more profit by using Loot scrolls (set to level 2) as well as agris fever points. These are very important to get good silver from Centaurs. 
You may also want to check some videos of another person on your class grinding there to see if you could for example improve your rotation or pack to pack movement. The Witch discord might be able to help you with that: https://discord.gg/zNWeZ8v

BTW witch is a rather slow-moving class best suited for more stationary spots, which is going to limit your income in Centaurs, since you will lose a lot of time moving pack-to-pack. Tagging a fast class is going to help you quite a lot. Musa, berserker, striker, etc.

Don't believe everything you hear. Some people make a sport of trolling others and then come up with stories.  Or they refer to old yt vids of some years ago, which ain't accurate anymore for the current state of the game. 

As far as i know centaurs was never a good place to get silver. Also went there myself with a couple a chars, like maegu, tamer and sorceress. Got a decent amount, but not billions no. 

Not sure if people still do it, but Aakman used to be the place for silver. 

You can see more real silver/h in link below. Find spot which is ~40AP below yours (200-230AP in your case). Then substract ~33% silver/h (you rarely have ideal class, all those buffs, scrolls on). Then the real max value is about 300+mil/h for your AP 200-230:

https://garmoth.com/grind-tracker/best-grind-spots

You can find Youtube videos with bilions/h grinding. Some of them are fake. Some of them are from players with maxed AP/DP, with all possible buffs, event drop rates on, scrolls on etc.

Also silver is calculated from items sold on Central Market. But sometimes you cannot sell them all, or you want to keep some of them for yourself (black stones, caphras etc.)

I can consistently get 1b~ in pure trash on Centaurs on Musa if I have agris fever. Even more with agris fever + agris coin. If it's loot drop event you can count some more in centaur belt's all though not much. 
It's a spot all about speed so you need a fast class, and to be able to one shot packs. I usually run foods/elixir that gives more stamina as that is the only thing holding me back from going even faster between packs as Musa. I have mid to endgame gear depending on who you ask.

OP make a musa, keep him tuvala timmy all pen, use lv2 scroll and agris and you can make ~700m from trash in 1h (need to be fast, and in 1h, 20k agris will not be consumed because you still need 10-30 minutes to reach the 20k agris consumed because that's how you calculate centaurs)

Why did you downvote this guy? haha. Centaurs are spaced. You need to be able to dash and AoE. All of the value comes from trash.

Witch would prol do well at Aakman. Aakman trash is too low, still, imo. Make it 20! At your AP tho you would shred more aaks than you would cents. Cents aren't an issue of AP, they are an issue of movement.

Silver per hour people talk about taking in account not only trash loot but also all other stuff you sell, in case of centaiurs mainly scrolls and yellow lootboxes with gems inside - put that all on market, then you will increase silver per hour you make.

Just from pure trash loot it takes about 40K to make a bil and I can't do it in an hour.  Youtube videos exaggerate claiming you can make that much including selling off Caphras, Relic Scrolls and other things you can post on the Central Market, but normally I will keep those things because I use them.

However, you need to use Agris with Collection Scrolls to have 7 manes drop per Centar kill.

Either way, for the GS, its the easiest grind for what it pays out.  Everything else pays less or is harder needing a higher GS.

Realistically, you should pull about 15K trash loot per hour which is about 300M silver, and you could make a bil by mindlessly grinding for 4 or 5 hours (I've done it before). 

Anyone else claiming more in less time is just flat out lying.