Why don't radios cost anything?

[Pepper]

This is a really minor point -- I'm just curious.
As you all know, only squads with a radio can call in artillery. Its a pretty nice ability, however, since you never know who will have the LOS on target. So as a general matter, the more radios you can have, the better.
Now, in game, only the x0 units (platoon leaders) have radios.
I noticed however, in setting up a PBEM, that you can buy 4 separate units (obtaining 4 radios, since each separate unit is a x0 unit) for the same cost as 2 sections of 2 units each (in which you get only 2 radios) for the same cost as one platoon of 4 units (in which you get only 1 radio). ...
So I find myself buying as many individual units as I can to maximize the ability of my troops to call in arty.
Maybe this is balanced in some other fashion (when you buy a section the leader has higher arty skill; platoon leader even higher still) but I'm not aware of it.
I'm not suggesting that every OOB be re-written to add a point or 2 of cost for individual units, but I was just curious if this was a built in "exploit" or if there is some design explanation.
Thanks.