What is the purpose of the 賣 (卖) component in the character 讀 (读)?
well, 賣(u+8ce3) is sell; while (u+27da0) is pronounced as "育".

left is 賣(u+8ce3), right is (u+27da0), note the difference of the middle component:



well, in the past, 賣(u+8ce3) is for 買賣 (buy &amp; sell) only. other characters e.g., 讀, 贖, 覿, 續 are using (u+27da0).



so, 讀 as a phonosemantic compound character is, combined "言" &amp; (u+27da0); that's why it's 屋韻﹒徒谷切

somewhere in time, the (u+27da0) is less used, and 賣 is more "popular"; which causes confusing.