Oh it should cost money, just a whole lot less money. The free play is designed to entice you into paying. If you really enjoy waiting 21 hours or more for a single move, come over and watch my grass grow. I won't charge you either and it is way more thrill packed.
I've reached the level (by paying) that I am seeing mostly unattended bases abandoned by the freebies. Of course it is in Boom Beach's favor to let me stomp all over free players for an extended period of time, I mean I did pay and all. Just as I am certain that they will probably at some point after I stop feeding them money to make the game increasingly harder upon me so I pay again.
You are correct though, there is a big disclaimer up there on the game's website proclaiming how this a "free" game. Of course it almost pokes fun at parents who didn't lock down purchases on their kid's iPhone/ipad. By the time the monthly credit card bill gets there, well is there a chart for how quickly a pre-teen can max out his mommy's credit card? Oh how that brings back the memories of my kids buying ringtones and them getting the cell phone bill slammed by strange service providers for voting on some dumb crap.