Here are the stats on each:
Wega 6.4 - $620 RoastE
- 190 Watts
- 1100 RPM
Ceado C7 - $699.99 WholeLatteLove
- 400 Watt
- 1400 RPM
Mazzer Super Jolly - $671 1st-Line
- 350 Watts
- 1600 RPM
Quamar M80 - 63mm - $499 1st-Line
- 330 Watt
- 1600 RPM
Quamar M80E Electronic Doser- 63mm - $399 - Stat Wise it is much better than the Mazzer E, has bigger burrs and costs $300+ less.
- 330 Watts
- 1600 RPM
The Wega's are overstock from Compak. The Wega 6.8 Conical I got new in July has a manufacture date of something like 2009. They are the older Compak body style grinders. The 6.4 is very underpowered for this price range though, so I would pass on it. The Ceado grinders are stepless, very powerful, extremely quiet and easy to maintain. The stepless feature is very handy for fine tuning espresso grinding! Both the Ceado and the Mazzer obviously command the highest price too. I would avoid the Pavoni, unless you get one used. You can easily find them on craigslist for around $100. I think the best bang for your buck is in the Quamar grinders. People in the US are not very familiar with them, but they are very popular in Australia. For that price I would personally go with the Ceado C7 or the Quamar M80E Electric Doser.
I would not go into purchasing a product this expensive with the thought of future resale value. If that is the mentality, why not just get the grinder you would trade one of these for in the future and call it a day? With that said, you would not have a problem selling any off the mentioned grinders in the future either.
Here is a video comparing the noise of a Ceado, Quamar and Mazzer grinding.