We stock/offer blue, red, green and black marble - the ones that come in 48" lengths - and sell mostly blue and black marble. We buy cases of these 4 colors to keep the cost down. If someone wants something else that comes in 48" lengths, I usually charge a little extra per trophy (50c or so) to cover the leftover and the additional cost per trophy.

I generally don't let them order anything that comes in 18" lengths without adding $10 or so to the order since there is a lot more waste with 18" columns and leftovers and additional shipping.

We don't display many trophies with columns and try to steer people toward risers as we find that he labor and stocking ferrules and checkrings, etc to be tiresome. This seems to work well and we don't sell many columned (if that's a word) trophies at all.

I also steer folk away from columns , there are so many better options to get height and I find columns pretty tacky. We stock a brushed gold , silver , some metallic primary colours and a few nice marbled ones. In my site under wholesale are the components we use
Tubes
http://www.tokerbros.co.za/new_page_22.htm
and also various "risers"
http://www.tokerbros.co.za/large.htm
http://www.tokerbros.co.za/small.htm

For those of you that show mainly just risers, what if the customer wants a 24" or so trophy? For the ones of you that don't want to stock supplies being in this business, just send your customers to me when they want a trophy with size!
We carry mainly PDU and keep the catalog out to show customers every choice available as far as figures, column etc. When a customer wants something different, we pull out all the other catalogs and search. Sometimes we may not make as much money from buying column we don't normally stock but we have made another customer satisfied.
We buy checkrings by the case (2000) at about 5cents or less each. $98.00 a case I think. Ferrules we buy by the bag (500). Threaded rod by the 1000. We stock around 15 or so different sizes.
Just a tip...... I have shelves in the back of the shop area near the miter saw that I keep the column on. I use the boxes that marble comes in to put the smaller peices in. On the ends of the box I have what color and model/name. When I get ready to cut an order I try to use the scrap first. Also as far as using the styrofoam boxes for column I use it for trophy figures as well. I used my vinyl cutter to letter them with "school" "baseball" etc. Those boxes stack nicely and there's always plenty of them.
Keep in mind, if the customer halfway knows what they want and they don't see it at your store, they are GONE! John