Wife and I have been doing some comparison shopping for a Reliance Generator Transfer Switch recently. We have pretty much settled on the unit; and Amazon looks like the source.
Bit, in three stores including Home Depot, Lowes and a chain retail store, which DID HAVE the same or similar transfer switches; sales clerks have steered us away from the "overly expensive" transfer switch. Instead they have promoted the sale of dryer plugs, or direct wired plugs, wire and a circuit breaker that backfeeds the house system.
Illegal, dangerous and a considerably smaller sale than the $250 transfer switch they have on the shelf.
Go Figure! This is the stuff that attorneys dream of.
RonB