Not sure if this is the right place for this or not as it's not a userscript, but I made a site with various calculators on it. It does a lot of the things I imagine a lot of RW traders and buyers do anyways, which is calculate which weapon is better, the 19% powerful 62.45 weapon, or the 24% powerful 58.91 weapon. Which weapon has a higher hit rate, a quicken weapon with more bonus or more accuracy, etc. It's all stuff you probably do, but packed together in one convenient place with sliders and interactivity. There's also an auction calculator coming up, where you can see the 'value' of a weapon by using a measurement that I use throughout the site which is % damage above a regular armalite. And how much money are you paying per % of damage over an armalite.
It's still in a fledgling state, but I want people to go ahead and check and give feedback if you're interested. Probably easier to hear from the community what's useful and what's not before completing the whole site, so it's a work in progresss. Also, I've tried to put the calculations at the bottom of the page so you can see how everything is being calculated.
Hope someone finds it useful!
Busta_Chrymes' Damage Bonus Calculator