Firstly: your water is not "EXTREMELY" hard. It's 17 gpg (grains per gallon) total hardness (this is what water softeners are going to be rated in, a gpg is 17.1 ppm).
You do want a softener before the RO system because hardness minerals will foul the membrane and require it to be replaced. Water softeners will replace the Ca+ and Mg+ in water with Na+. Sodium is easy for RO systems to remove.
When you look at water softeners, you need to look at the total capacity in 'grains'. If you're a family of 4 and use average amounts of water daily (75-100 gal/person/day) you're looking at (say) 350 gallons * 17 grains per gallon = 5950 grains of hardness you need to deal with daily. My softener is rated for 64,000 grains total capacity. 64,000 / 5950 is approximately 11 days water usage between regenerations.
Now, a little more on water softeners, capacity, regeneration, and all that jazz. You can think of a water softener like a battery. The 64,000 grain (or whatever) capacity only applies if certain conditions are met: a certain amount of salt rinse for a certain amount of time. This is usually a large amount, in my case around 16-18 lbs. You can cut salt by 1/3 to 1/2, say 10 lbs, and still get 80% of the capacity of the resin. That last 20% requires more and more salt to access. So in common practice, you de-rate your total capacity by about 20%. The softener will still remove 100% of the hardness, but will do so for a shorter amount of time: you didn't charge it to 100%, so it will 'run down' faster than it otherwise might. That is okay. Do not expect to get 100% of the rating of your water softener.
I was pricing softeners on Amazon and they run from $700-1200 in this capacity range, depending on other features not germane here.
Now on to RO systems.
The $1500 small industrial systems are for whole-house use. This is overkill and unnecessary. You don't need RO water to flush toilets and shower with. If money is no object, go for it, but I would simply install a small unit that feeds a mini-pressure tank and then run 1/4 lines to your fridge/ice maker and a drinking water/cooking faucet. These can be had for $250 or less.
In short, you can have fully treated water for your house for $1500 or less.