You will get a better price for ebay auction titles that state (clean gold plated pins) etc. The reason is that the tin has to be dealt with, and for some refiners that means a pre-soak in a different acid to dissolve the tin, then that also means an extra wash and incineration step. If the refiner doesn't know to deal with the tin first, when dissolved in Aqua Regia they are going to create tin oxide, which is insoluble and takes extra steps to convert back to it's metallic state.
Another thing a lot of solder contains is lead. Lead is also a you know what to deal with. It might take an extra step at the beginning, or the addition of sulfuric acid to the solution to precipitate the lead so it's not melted with the refined metal. It's better if there is no or little solder.
Anything you can do on the scrap side, that makes it easier and more profitable for the refiner, is going to bring better prices, if you are selling to a refiner. That might not be true is you are selling to a scrap yard that pays out on pins, but then if you are doing that you are getting far less than the actual value and should be slapped. (just kidding, just had to slip that in there I'm usually not like that). If there are two lots of gold plated pins on ebay, considering what I have just said pretend you are a refiner and you are looking at the two lots, one is $70 and are not clean, they have solder which adds weight and can be a you know what to deal with, and a lot for $99 that were totally clean of any solder. Which are you going to buy? Answer that, and you answered your own question. Or better yet, search ebay for pins, and then look at each lot and decide for yourself which you would purchase, then try to make yours look that good.
Scott