kind of a dumb question of you to ask... you make money like you do in any game.. and no, you will have to buy them at that price, or somewhat lower depending on your merchandise skills... but you do not HAVE to buy those pricy books now, you're like 0.1% into the game.. just leave and come back later.
As written in the game guide thread, to make money simply loot and sell everything and make sure you set buy/save prices at max through haggle (max being dependant on seller's skills and yours)
The hunting books allow you to get more trophies from animals, which can be sold or used in alchemy. some mobs, like the gorger which you will encounter later, drops a lot of good sellable stuff if you have all the books, allowing you to earn close to 100 gold per gorger. but again... this is for much later in the game. just take your time, money will come in time.