I have 8 acres and the 2500 sq ft house and it is valued at only $145,000. This is rural Maine though and thats about average for a home.
Back to the meganobz, a great use for them is at mid level games. A unit of 4 in a trukk is only 200 points. It is fast, should have enough other models around to break up shooting, and can offload 16 S8 WS4 attacks with 8 wounds and a 2+ save. Really a dangerous package and similar to suicide Terminators. I would give a couple skorcha add ones. Skorchas are really a great choice. I never buy rokkits.
I would have thought the main use for meganobs was to take on hard enemy units who don't have a lot of power weapons and ideally have no powerfists. Then just charge them! Admittedly most of these units are not particularly mighty in combat, but some units can throw a bucket load of regular attacks against you, or have good armour but poor attack values. Im thinking things like other orks, most eldar, guard, most normal marines, all tau units ever, most tyranids that are not MCs/Rending/Bonesword armed. Actually there is quite a lot out there they are better than regular nobs against.
Obviously the main reason to use them is the great models
Thats often why I include things that are not supposedly brilliant!
Off topic: By my rough calculations I have around 1000 sq ft space in my house and 1300 sq ft garden. This is large for my town and especially considering it is only worth about £86,000. Its only due to the "quality" of the area I live in though. If I lived where my parents did, their house and garden was smaller than mine but the house was worth £150,000.
My second largest bedroom is my games room. It fits chairs, a pc and 6x4 foot gaming table, all the terrain etc we need and most of my models are stored in there. I couldn't fit an 8 foot wide table in there though due to having a strange shaped room, with the chimney going through it.
What I mean by all this is Philly is very lucky!