This one costs approximately nothing. Unless you furnish it, of course.
We all have our favourite spot to sit and relax, maybe read, watch TV or just curl up when we're feeling under the weather. Mine is the end of the sofa closest to the kitchen (and yes, now I think about it, the fridge). It's like having 'your' side of the bed - your little nesting site is just that. Yours. Not that I'm territorial. Other people are allowed to sit there. This isn't a school staffroom or anything.
It's where I lie in winter under a woollen blanket, nursing a hot drink. In summer I collapse there, grateful that the sun shines on the back of the house for most of the day so the living room's always cool and a bit shady.
Of course, the nest of my dreams would be somewhere entirely different: maybe a porch swing complete with cushions, a book, the sound of crickets and a mint julep close to hand. Or a fireside nook with views over a lake and a ticking clock for company. But for now I'm happy with what I've got.
I mentioned furnishing (feathering?) your nest. For me, there are a few nest necessities. Sheepskins. Cushions. Good - but not too harsh - lighting for reading. A cosy throw or blanket. And a little table for drinks, reading material, knitting... and the TV remote if you manage to commandeer it.