I have seen this argument played over and over again - usually by those that have played enough to know but not enough to know better (I am not excluded from that list - see previous posts).
I rarely use towers - (probably because I am more offensively focused) but have seen them used effectively.
As for pill boxed - they are excellent - just dont buy ALL pill boxed on a border - by 50% - especially on the edges - an you have increased you ability to kill a unit in a single turn by having more units shoot one target.
They all have their place.
To change the cost of a tower (say to $3) would could mean that every game ends in a whole series of towers over a map.... not sure
(as I said - I rarely buy them - because I think the good players know how to kill them quickly - but - rextrent has used them against me many times and stuffed up my attack plans -its all about the map geography - forrest, mountains - deserts etc.)
Play the top 20 and you will learn some neat tricks. (Morn has one special trick I promised never to mention again - all I can say is watch out
But all these discussion stimulate the imagination.
The game is fine as it is - its balanced - fun - and addictive.
If its not broken - dont mess with it.