Whilst not defending the cost, I think the Silent Guitar has a couple of benefits over "a cheap electric".
It feels like an accoustic (neck/set-up), it breaks down and fits into a small bag, it doesn't need an amp (earphones fit directly to guitar) and, as with the version I tried, it's also available with nylon strings.
I used to travel a lot and did, on occassion, take an electric guitar for "silent" practice. As well as the guitar I needed my effects pedal (to use as a small amp), earphones, power supply and 2 leads. Eventually I found I would rather visit the music shops in whatever town I was in and pretend to be interested in buying for an hour or so!

C-flat.