It's called a semi-acoustic. I don't know where you are so I can't tell you how much one might cost in your area. It doesn't play like an electric guitar as such, just as an acoustic with pickups
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Since acoustic guitars are hollow-bodied, and electric guitars are solid-bodied, it would be hard to manufacture an interchangable guitar like you are describing. Especially since electrics and acoustics use different strings and bridge/neck adjustments.

Acoustic-electric guitars you see around are simply acoustic guitars with pick-ups in them in order to amplify the acoustic sound.

As far as price goes, like any guitar, you get what you pay for.
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If you play gitar loud enuf U can heer all the vibratins from the stringz evin if u dont want to git a amp machine as long as the gitarr haz a hollo areah 2 alow souund pentraton thru the body of gitar. but that for toy gitar,,,,,,,if u have reel gitar yu can canactt it 2 the amp masheen to giv morr powre and soundd
tri som gitars lyke fendar or maybee a eybanezz strat

grate luck in the band ur inn!!!!!!

IM happee 2 helpp u n-e way i can
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i play gitar in the band 4 manee yeers inn scool