I work in the real estate industry and a lot of people look into the home flipping market with dreamy eyes thinking that's how they'll get rich and fund their retirement nest egg. Yes, some people can do it right and make a profit, I imagine the same is true for airplanes, however as many risks as there are with cars and houses, that's only further magnified with planes as the costs for just about anything are astronomically high and if you are not a legal professional there is very little work you can do yourself. What kills me is when I see an old 172 with a 160hp engine with a whole fleet of top of the line avionics... you will never recoup those costs.
A large part of it depends on what you consider "refurbished" and what will actually bring a return. A beat up old 172 might be able to turn a profit if you can clean it up and have a good network of contacts to give it just the right amount of updates to sell for a little more than you bought it. Make sure everything works, give it a nice wax job, reasonably update some avionics, and I bet you'd be in business. But, while a plane might take more than a coat of paint there are people who flip houses for decent profit by just replacing carpets, doing some paint, and a little bit of landscaping... what they *don't* do is take a mid-low-range house in a mid-low-income neighborhood and dump it full of Viking, Wolf, and Miele appliances and spend $75K installing a pool <- that's what I think of when I see an ancient high time 172 with top of the line avionics.
Problem is, I think most aviators get too emotionally involved in their hobby to effectively turn a profit, to make money you kind of have to shut some of that off. "Would this house look sweet with a Viking or Wolf range? Yes!" but will I recover those cases. Hell no! Install that standard GE range from Home Depot for $600 and get the house sold!!
Depends who you would sell it to and what kind of planes you refurbish. Planes with a loyal fanbase like Bonanza, Mooney, Cubs, etc., I bet that it is true, you see the same with boats. But I am sure there are also new low time pilots out there who would love a Warrior, Cherokee, Archer, Arrow that wasn't completely shredded and falling apart at the seams...