The 4EXT recovery itself is free, you just have to download and install it manually. There is an app that will install it and allow you to control it, that is what costs $4.
Here is my take on the recoveries...
There are two you should be concerned with... 4EXT and TWRP2, both are touch screen and both and an app to install and control them (at least to some extent). I have heard it said that 4ext does a better job flashing, I have yet to see anything amiss, and there has been an update recently that may have balanced it, IF there ever was any difference.
On Goomanager, use the menu button, then settings, install opensource recovery, that will install TWRP2.
If you plan to go S-off
I would recommend TWRP2 and GooManager to install and control it. Several roms (JMZ, Midnight, Harmonia) all use GooManager to handle updates, and this really makes things simple for users and devs. GooManager users running Harmonia get updates about 15-20 minutes before everyone else (I.E. they can download before the rush).
Yes, you can use GooManager to download the updates and then flash with 4EXT, but to me, that just means another app taking up space. And some people who use Harmonia simply remove Goo Manager and just handle updates themselves and soe roms have no update system or a custom one. So it's up to you amd how your rom works as to how you want to do this.
If you are not S-off
The above still works, since many roms still use the stock kernel (or work fine with it), so it not flashing with the rom is not a big deal. If you want to use anything other than a stock kernel (*Harmonia uses both modded and unmodded), then you will need 4EXT's kernel flashing ability.
*Harmonia comes with Mobsterguns' kernel, but if it doesn't flash, you will only miss out on a small boost in percentage, it's more of a bonus. If you leave the stock kernel, everything will still work fine. The same applies to any rom using his kernel. This backwards compatibility was one of the very reasons I decided to use it.
And yes, I use GooManager and TWRP2. It works well and has greatly simplified my rom updating.