just to make you feel better about the logic of it all (or maybe not), I will tell you that OED gives both spellings and pronunciations for the noun (i.e., height, heighth) and goes on to say: In ME. the forms in -t were predominant in the north, and since 1500 have increasingly prevailed in the literary language; though heighth, highth were abundant in southern writers till the 18th c., and are still affected by some. The stem-vowel has generally been U, ey, ei, though forms in i occur from 13thc., esp. in northern writers, hicht being the typical Sc. form from 14th c.; in Eng. hight is found from 15th c., and was very common in 16th and 17th c.; highth was also very common in 17th c. and was the form used by Milton. The hei- forms come lineally down from OE. (Anglian héhþo); the hi- forms are due in the main to later assimilation to high. Current usage is a compromise, retaining the spelling height (which has been by far the most frequent written form since 1500), with the pronunciation of hight.]