The price range for Book Building Public Issue was set by the company that came up with it. The price range usually includes a higher and lower level.
The floor price is the lowest level at which an IPO can be offered.
Book Build IPO investors can bid at any price within the price range set by the company. Retail investors can also choose to bid at a "Cut-Off price" during the Book Build process.
The investor can pay any price the company decides at the end. The Cut-Off price is the price that retail investor must pay to place a bid. If the final price for IPO as decided by the company falls below the maximum price for IPOs, the remaining amount will be returned by the company to the retail investor.