Here is the tinker scrounge point of view. I bought a Russian military surplus rebreather, $1000, convert to mCCR $2000. End of discussion. I pay about $75 for 40# of sodasorb, I get O2 for $25/250 ft3--this costs about so about $15 per dive. You may want some training, and if you buy a new unit chances are it will be required. If you are considering a RB you will have a stage set up sitting around, so you don't need to buy that again.
Then I bought a rEvo, this was about $7k, and the training was included--this was a special offer. I think $1400 is retail for this training.
There are some benefits to RB diving--You have "perfect nitrox" or trimix a each depth so your NDL is generally longer or your decompression is shorter. Your gas consumption is depth independent. If you are using helium, then you may save a lot of $$$. The first time I dove a RB was almost as profound as as the first time you breath underwater OC--Silent, no bubbles. Fish love you--I was followed around a lake by a bass for about an hour.
I am selling my Orca for less thank $2000, add a couple of parts and you would have a nice working mCCR--say less than $2500.
Where their is a will there is a way.
Of course there are cheaper ways of killing ones self, be careful.