In my honest opinion, no it wouldn't be feasible to launch a ghetto blaster store. There just isn't enough of these ghetto blasters around to support a business that has to pay wages/rent/bills etc. These pictures you mention, with 100+ ghetto blasters displayed, represents many years of searching and many hours of resoration to return them to a good visual state. A proper company looking to trade in these ghetto blasters would have to find this number, if not more, each month or so I reckon, depending on buyer demand. Otherwise it would go under. There just isn't enough good, cheap, ghetto blasters available to support such a business.
From another point of view, it depends where your business is based. If you live in an area where living costs are relatively low, it may be feasible to sell these ghetto blasters with a view to making a profit. It also depends on who buys them, and what they're willing to pay.
But generally, there's got to be a time in the not-too-distant future when these ghetto blasters become so rare that they cannot even be found anywhere, let alone be found in quantities that would justify running a store that relies on sales to survive.