depends on you're idea of expensive, but i was able to cut cost by shopping around and doing some stuff myself
a 20 foot 30 amp cord will run you 50 bucks
i was about to buy both end for 9 dollars a piece, and wire for about 50 cents a foot, end ended up making that cord for 28 myself
the interlock was 30
the inlet box was 64
then some odds and ends, the 30 amp breaker, dont quite remember, 25 bucks?
and some wire to run from the inlet box into the breaker panel, and the conduit it runs through...another 50?
that puts it at right about 200 bucks
plus however much you got in the generator itself, in my case, about 600 bucks
oh, and however much it was to pull a permit, i dont remember how much it was, but you really want to do that part to cover your butt
