Check the condition. Refurbished watches are not as valuable in the collectors market. It is better to have a watch that is slightly discolored or a little dirty. Some people feel they just want to buy as many watches as possible. They don't necessarily look at the actual quality.
Condition makes a big difference in the price.
On the whole it is much cheaper than paying a dealer at retail. The movement should be serviced once every two years or so. Take it to the manufacturer or someone reputable. They will seal it correctly and they will know how to clean it - there's a cheap way to do it, by dunking them in a cleaning solution. But when watches are serviced right, they are taken apart and cleaned and put back together again.