To each his own, but I would personally not spend $900 for a 1:1 waste to product ratio. Not unless I had an exceptionally large aquarium or exceptionally expensive tap water.
Figures for how much water costs vary from $1.50 to just over $3.00 per 1,000 gallons in the US. We'll use the more expensive estimate of $3.00 per 1,000 gallons. Let's say you have a 100 gallon tank. You do two 20% water changes per month. That's 40 gallons. Let's then assume that you need 1.5 gallons per day for topoff purposes. That's another 45 gallons. Let's say you use a miscellaneous 10 gallons of water for cleaning and soaking dirty pumps. In total, you need 95 gallons of deionized water per month. If your system uses a 4:1 waste to product ratio, you need 5 gallons of source water for every 1 gallon of purified water. So in total, that 95 gallons of deionized water requires 475 gallons of tap water.
If your tap water costs $3.00 for every thousand gallons, 475 gallons of water will only increase your water bill by $1.42 per month. At these prices, your DI water costs you only 1.5 cents per gallon. And that includes all the waste that went down the drain.
A 1:1 waste to product ratio will save you money. Instead of 475 gallons, you'd only need 190 gallons of tap water to make your deionized water. With this kind of system,your aquarium would only increase your water bill by around $0.57/month. If my estimates are correct though, you're only saving less than one dollar every month with a 1:1 unit as opposed to the traditional 4:1 unit. At a price of $900, a 1:1 system would take over 83 years to RoI. Even if I'm a thousand percent wrong, you still won't RoI on a system like that for over 8 years.
The EPA estimates that the average person uses up to 100 gallons/day of water. That's 12,000 gallons a month for a family of four. A RO/DI filter with a 4:1 waste to product ratio would only account for 3.96% of your monthly water use if you're anything like the national average. I am not advocating that people be intentionally wasteful or that people should not look to conserve when possible. I just don't think that a 1:1 waste to product is worth the money. Not when RO/DI waste represents such a small amount of the average family's water use.