K3vin
To answer honestly, if it were my shop, I'd be hard-pressed to order 100 of anything unless I knew I was capable of moving it quickly. If it's a small shop (such as the one I have locally), chances are they'd never break even on such a purchase because they promote their biggest profit maker, which is the eGO starter kit (2x 650 mah batteries, 2 tanks, a charger, carry case and one juice of choice - 10 ml) for $59.99. Unless someone knows about the mod or asks about it, they recommend the eGO's and from being in there almost daily, I'd estimate 90% take that deal.
That said, I know this is an example, so if I were to buy 100 @ $35, I'd have $3,500 in them. Since most full kits are selling for $49-$59, I'd price mine around the same and net $1,400-$2,400 in profit from the sales and re-invest accordingly. From a business standpoint, and given how technology is ever-changing, I'd rather run out and guarantee them in-stock in a few days than to over-order and get stuck with them. That's the nature of retail though; you have to factor in shrink costs too, but buying to sell instead of buying to stock helps to reduce that.
For juice, everyone marks up juice costs well beyond 200% I'm almost positive (no way to confirm that, of course - no insider info

), but....I'm not a wholesaler nor do I have access to discount pricing and I can make the exact same flavors (based on taste - I have no idea who they go through for flavors) for $0.50 per 5 ml (including shipping costs and the bottle), it's hard to account for ~$6-$8 being time/labor and cost of getting it out there.
Profit margins from juice make up for the lower profit margins on upgrade sales.