From the SFAs rules for the Scottish Cup:
35. Minimum Charge for Admission
Subject to a minimum adult non concessionary charge for admission to matches in the Preliminary Round (if applicable), Round One, Round Two and Round Three, of £5, and of £8 for matches in subsequent Rounds excluding the Semi-Final and Final Ties, the charges for admission shall be arranged by the competing clubs. If they are unable to agree, the charges which are normally made for the regular fixtures of the club at whose ground the match is to be played, will apply.