Any Advice for Running a Solvent Commodity Broker in New Magincia?

Does anyone have good advice for how to run a commodity broker in New Magincia, one that actually stays solvent?  

If you set up one of these brokers, the game automatically deducts for itself 5% of every purchase or sale and there is a weekly fee of 5% of the total sale price of all sellable inventory.  

I had one of these brokers set up on Balhae for a few weeks, with the price that players pay to buy from the broker set at 17% more than the price that players received if they sold something to the broker.  Unfortunately, what I had happen a few times is that people would sell the max amount I was willing to pay to the broker, which would use up most of the gold in the broker account.  But then that commodity would just sit there unsold because I was also willing to sell that commodity but apparently no one wanted to buy it.  So the weekly fee on those unsold goods would demolish what other gold was left in the broker account.  In about two weeks' time, I lost 3-4 million on the broker and was unwilling to keep it going at that rate.

My guess is that maybe the best thing to do is to just set up a broker that will buy commodities from other players and don't even try to sell anything, especially on a low-population shard.

Any thoughts on this from anyone else?  I had really hoped to set up something that would be of use to new/returning players but I'm unsure of how to go about it at this point.  I guess selling stuff in hopes it helped EJ players wasn't going to work anyway because the brokers always sell items in the form of a commodity deed, which EJ accounts wouldn't have been able to redeem anyway.

I think the brokers are a great idea.  I'm just not sure how to make one work, especially on a shard that doesn't have a very large population.  @Kyronix, if you have any ideas, would love to hear yours too.

These are the buy/sell prices I was using, first amount being what I sold things for to a player and second amount being what I paid to buy something from a player:

darkglow poison 878 750 exploding tar potion 164 140 fear essence 246 210 parasitic poison 586 500 potion of invisibility 82 70 saltpeter 112 95 shatter potion 410 350 black dragon scales 118 100 blue sea serpent scales 54 45 green dragon scales 176 150 red dragon scales 82 70 white dragon scales 48 40 yellow dragon scales 24 20 valorite ingots 878 750 verite ingots 528 450 agapite ingots 410 350 golden ingots 142 120 bronze ingots 234 200 copper ingots 164 140 shadow iron ingots 264 225 dull copper ingots 66 55 iron ingots 16 13 frostwood boards 352 300 bloodwood boards 118 100 heartwood boards 88 75 yew boards 30 25 Ash boards 14 11 oak boards 10 8 boards 4 2 high quality valorite granite 1170 1000 high quality verite granite 1054 900 high quality agapite granite 762 650 high quality golden granite 644 550 high quality bronze granite 528 450 high quality copper granite 410 350 high quality dull copper granite 294 250 high quality shadow iron granite 936 800 high quality granite 176 150 enhanced bandage 18 15 green thorns 54 45 orange petals 154 130 petal of the rose of trinsic 48 40 powder of translocation 1000 854 red leaves 54 45 smoke bomb 118 100 a small piece of blackrock 294 250 blight 1638 1400 corruption 29250 25000 muculent 2340 2000 blue diamond 5266 4500 brilliant amber 3276 2800 dark sapphire 11700 10000 ecru citrine 2926 2500 fire ruby 3510 3000 perfect emerald 1170 1000 turquoise 4680 4000 white pearl 15210 13000 abyssal cloth 10648 9100 bottle of ichor 2048 1750 boura pelt 2926 2500 chaga mushroom 586 500 crystal shards 17550 15000 crystalline blackrock 6552 5600 delicate scales 574 490 enchanted essence 136 115 essence of achievement 3978 3400 essence of balance 3276 2800 essence of control 11700 10000 essence of diligence 4096 3500 essence of direction 3510 3000 essence of feeling 1170 1000 essence of order 11116 9500 essence of passion 8190 7000 essence of persistence 2926 2500 essence of precision 11700 10000 essence of singularity 7020 6000 faery dust 8190 7000 goblin blood 1464 1250 lava serpent crust 4680 4000 magical residue 60 50 raptor teeth 5850 5000 reflective wolf eye 586 500 relic fragment 2106 1800 seed of renewal 7606 6500 silver snake skin 13456 11500 slith tongue 200 170 undying flesh 586 500 vial of vitriol 936 800 void orb 17550 15000 zoogi fungus 352 300 Arcane Empowerment 30000 25000 Attunement 30000 25000 dryad allure 30000 25000 essence of wind 30000 25000 ethereal voyage 30000 25000 gift of life 30000 25000 gift of renewal nature's fury 30000 25000 reaper form 30000 25000 thunderstorm 30000 25000 wildfire 30000 25000 word of death 30000 25000 Arcane gem 88 75 pieces of barbed leather 176 150 pieces of horned leather 118 100 pieces of leather 30 25 pieces of spined leather 60 50 tiger pelts 820 700 copper wire 936 800

It's a frustrating system, "most" of the stalls on Siege are buyers at dirt cheap prices.

First step: do it on a shard with a viable population.