if you have a look at some of their models you might find something close to the one you are going to build and get a good idea of weights for various models.
I've had a look.
The total dry weight for the Ranger slide on camper is approximately 800Kg. Any options fitted may increase the overall weight.
Yikes, that's heavy, but then
The total dry weight for the Cruise-n-Snooze camper is approximately 200Kg. Any modifications may increase the overall weight.
No bad, nowhere near the features of the larger units but nice and light.
No prices though
you mentioned water but not how you intend to filter/sterilize it
In the past (for over 10 years now) we've had two filters, a 20-micron for sediment to produce "fresh" water followed by a 0.5-micron silver-impregnated carbon filter for drinking water. But we only have a single tank, we don't separate the fresh and drinking into different tanks so that system works well.
In the Cruiser I will have separate tanks so have to think about what to do and UV may be the ticket.
$310 is a lot but only a one-off so OK, but the annual replacement of bulbs will cost another $71? Actually that's OK as well, the carbon filters we currently use can cost $40-60.
One other thing is how will you turn on the power? If it's working "on demand" you would have to flick a switch every time you use the tap.
I do like the look of them though, it's worth putting some thought into it.