I am currently running a large desert mining operation, which means I can produce these materials in bulk. I have set up a exchange-style shop at /v 511 with each item along the wall. The prices are based upon statistical analysis of 4 major SMP1 shops. So, come on over to /v 511 if you need lots of these materials in bulk.
I haven't necessarily checked it out yet, correct me if I'm wrong; but when you are selling items in bulk I highly recommend you don't use mall prices. Mall prices are generally expensive simply because they stock every item. If you are a specialty shop and only sell these items, I suggest you go lower than the average mega mall price; probably around the price that suppliers sell for. Just my tips
I usually say 1r above average sell-back price per stack, considering it's only 3 item's you'll be selling, not to mention in bulk
Yow, I would lower your prices a bit, because I know a bunch of malls that sell cheaper. Just saying, if you want my business.
Yeah, you should probably lower your prices. Sand goes for 15r a stack when in bulk, sandstone for 70r a stack, cobble a mere 20, and glass about 25-30.