Bible scholar Spiros Zodhiates has a interesting footnote for Malachi 3,7-8 in his "COMPLETE WORDSTUDY OLD TESTAMENT" which states..." This passage is often used by those who advocate “storehouse tithing”; that is, bringing the “tithe” into God’s storehouse (the local church), rather than giving it anywhere else. They suggest that gifts to ministries other than the local church should be above the “tithe.” Certainly the “storehouse” in Malachi represents the temple or a building in the temple complex. However, the Old Testament “tithe” or “tenth” cannot be reasonably equated with ten percent of gross salary or wages which most people earn today. Above all, giving should be a matter between the Holy Spirit and the believer, not a regulation. The “tithe” may be an adequate guide for determining how much some people could give (indeed, for many in a prosperous society, it is probably an inadequate level), but the amount of giving must be a personal decision. The Apostle Paul wrote that God examines the motives for the giving, not the amount (2 Cor. 9:7)."
Zodhiates, S., & Baker, W. (2000). The complete word study Bible: King James Version (electronic ed.). Chattanooga: AMG Publishers.