@TS Epiphones are not expensive.. if youre talking about the NY era epis from the 60's, that's a different story (They command a good price in the vintage market). The Gibson knockoffs are much cheaper, about $400-700 and the ones made in japan during the 90's would cost a little more because they're supposedly built with stricter quality control.
a brand new Gibson costs about $2k-5k depending on the model. Historic reissues generally cost more than their modern counterparts. The ones mentioned earlier are vintage ones and there's a reason why they cost that much (rarity, demand, construction, material used back then, our guitar heroes used them, etc etc).
If you are just starting out, I wouldnt worry about why guitars are priced as such. Find a guitar that works for you and is within your budget. Welcome to Philmusic!