I currently have room to buy about 6 stacks of gold bars in my shop on smp5 if you are interested, I think I buy at 10r each. Hope that helps a little. I buy gold quite frequently so I always try to leave some room in the chests for buying.
you can try messaging the big shop owners on your particular server and see if any of them use bulk suppliers. on 6 theres like three people who do supply runs for me
I've been playing on here for awhile and I'm a little out of touch with the economy aspects of the culture here but back when I first started it was like a rite of passage for all new players to build a store. The most successful stores were the ones that could keep diamonds in stock. This was way before there was a promo market and all these other rare items. Everyone just wanted diamonds. All that to say that if you want to take part in the economy on EMC, and it sounds like you do, then you should build a shop. If you aren't much of a builder then it can be a very simple structure or simply put chests down on the grass on your res. Advertise your shop on the forums in the Product section and if you have good stuff at a good price it'll sell. I really don't think it'd be hard to sell any ores or items that come from ores. You'll have a much harder time selling any of the more common blocks. I know back in the day anyone that could keep a DC of the various colors of wool would have a successful shop, although those aren't as profitable. Also colored glass blocks and panes would probably do well. Basically anything that you have to WORK to get in this game sells well or anything that builders need in bulk. Anything that is simple simply won't sell because everyone already has some.