A is an extremely desirable letter and increases the value of an LLLL.com considerably, especially if it's the starting letter.
If you go to acronymfinder.com , you can get a few good ideas of why an LLLL.com starting with an A may go for more than an LLLL.com starting with a different letter. Some of it's benefits include more possible acronyms + more frequent usage in the English language.
There's way too much to cover in a post about what affects the value of an LLLL.com, but some basic facts:
Pronounceability: (in general, CVCV > VCVC > CVVC > VCCV > ordinary LLLL.com)
Starting Letter: (A, C, S in example command premiums - Q performs poorly here)
Ending Letter: (A, C, I, O in example commaind premiums, Y performs poorly here)
Letter Quality: Quad Premium > Triple Premium > Double Premium > Anti-Premium > Single Premium. Premium letters include: A,B,C,D,E,F,G,H,I,L,M,N,O,P,R,S,T. Weaker Premium Letters include: F,H. For lesser quality letters, the pattern appears to currently be: W/U > V > K > J/Y > Z > X > Q .
Letter Pattern: For any letters A,B,C, D we generally have: AAAA > BAAA > AAAB > AABB > AABA/ABAA > ABBA > ABAB > AABC > ABCD