The most common color I have sold is white (see image). While white and black are the most common colors, the more colorful special edition controllers sell faster and fetch a higher price. I have compiled the numbers to try and determine if fixing old controllers is a viable business model. If you exclude labor, you have the cost to acquire the controller, the parts to fix the controller, the cost to package/ship, and Ebay's transaction fees. Total gross sales (minus tax and Ebay fees) were, $565.88. That may look like a good number, but after subtracting initial cost and shipping, you end up with a $157.97.
That money then goes into buying replacement parts and more broken controllers. My average cost for a non-working controller was $14.21. That includes tax and shipping. The most I have paid for a non-working controller is $16.44. It is getting more difficult to find controllers for less than $16 unless you buy 3 or more at a time or find someone who wants to get rid of a broken one quickly. On auction sites, I find the same people bidding against me on every controller listing. We are just making each other's resale business less profitable by buying untested controllers for more than they are worth. I suspect the other bidders are relisting controllers on Ebay for parts or not working at a slightly higher price. The proof is that the average price of a broken controller on Ebay has increased dramatically in the last six months.
So, despite the satisfaction of getting a controller to work again, the reward just isn't enough to justify the time it takes to find fixable controllers at a reasonable price. There are also issues with older controllers that make them impossible to recalibrate. Microsoft recently gave the ability to recalibrate Model 1914 controllers but have only released firmware updates for older controllers to make them more tolerant to stick drift. Eventually, thumb sticks are going to wear out. High quality analog sticks are more expensive and only have a life cycle of 2 million cycles at best. With a popular fps game like Call of Duty a thumb stick can wear out in 3 or 4 months. It would seem like the ideal scenario for a controller repair shop, but people are trying to sell their broken controllers at a high price and pay as little as possible for ones that have been refurbished.
The other issue is that after a while you end up with a bunch of controllers that are unfixable because of circuit board issues. They either won't turn on or the buttons and triggers don't work. I currently have 5 controllers with various circuit board issues. Buying a used circuit board cost as much as buying an untested "for parts" controller. You need to have some spare parts, but over time you end up with a collection of controllers that have bad circuit boards. Every year more gamers upgrade to newer video game systems, which means that the market for older controllers will gradually diminish. Eventually the only people buying old controllers will be collectors who are trying to acquire every variation.