Outside the personal biasness and religeous side of things, its not as bad as you think. That is - IF YOU PLAN ahead of time. Meaning - know what you plan to keep as it relates to fish and coral. That will give you a up front estimated cost for buy in. Here is why.
1. Coral dictates lighting requirements. Sps vs softies, etc.
2. Coral dictates supplements (DT's in your example, idodine, etc)
3. Filter - biasness aside you don't need mechanical usually - live sand and rock work
With that in mind - live rock and sand bed are your filter. You just need water movement in the nano's. Koralia's or other power heads work - that isn't too bad. Heater - ok, not bad cost wise. Mike's filter is ok - remove the media if you want and just use it for water turnover, etc. Your good.
Fish - green chromis, clowns, royal gramma, six line wrass, tri blenny, etc - all great fish. Nano = small bio load. Add a couple snails, cleaner shrimp or peppermints - your set. Again - no supplement needed here.
Corals - small polyps, softies, etc - most won't require DT's. Green star polyps or xenia - yeah - they need it. Depending on what you are housing will depend on supplements. You may get by with DIY stuff such as vodka or other things - I don't know how crafty you are or time.
Lighting - as with corals above, MH cause heat so vho's or other options are better. Highest cost factor is here so maybe consider a DIY. LED's are gaining especially if you go your own route. Meanwell drivers or buckpuks drive 8 to 6 led's - choose white, royal blue, etc - you can pinpoint light as you deem necessary and growth patterns so far have been positive. If you want - stay with PC or svho's or overclock standard florecents using ice caps.
What I mean is that if you see ahead of time what you want to keep the cost will vary. It can be done cheep. My 16 year old daughter build a eclipse 6 gallone for under 100 bucks. Granted she pillaged my main display and sump - but it worked. Most expensive was the LED light she tried from sunburst which was 60 or so bucks. Tank was 40 bucks on sale. Rest she stole from my setup. 4 cups of live sand, 2 large rocks, some rubble, mated pair of clarkie clown fish....off she goes happy as a clam
I dunno. If you didn't already catch it - planning is essential
Knowing what coral you want to keep in turn feeds lighting requirements which in turn feeds into any additives. Fish - well, that is the easiest of all because you have a set amount of realestate which means no tangs, etc.
BTW those cubes you mentioned are pretty crazy. I think they have a higher upfront cost. But...if you google them or read up on them around the community - they have many that look freaking awesome.
Your mileage may vary of course. Seems like Mike is trying to make it easy so all you have to do is pick fish and coral.
