Basic Price List Functionality Still Missing

Basic Price List Functionality Still Missing

I am having a problem with the most simple imaginable pricing scenario - you buy cheap, add profit, then sell high.

Or in less simplistic terms: business buys a product at a given cost, then adds predetermined percentage markup, and finally sells that product at that higher price to some group of customers.

Let us imagine that I have a simple reseller business that sells widgets.

I just started so all I have is 3 items that I buy and sell:
widgetA, which I purchase from my wholesaler for $10
widgetB, which I purchase from my wholesaler for $15
widgetC, which I purchase from my wholesaler for $20

I calculated that in order to cover my overhead and make a decent profit, I need to MARKUP my widgets' PURCHASE  cost by 30% before selling.

How do I set-up this process using Zoho's New Price List alone (so no spreadsheet imports please)?