Im afraid to say that the prices for liverock on a tank this size will probably be many times this amount.
The reason for this is because standard aquarium sized liverock will look like tiny pebbles in a tan of the size you are designing. You will need rocks that are specially collected (by crane usually) and then delivered to your doors and again usually craned into the tank as this is the only way to make the tank look natural. So you will need a special grade of rock size (expensive), handling and shipping with cranes at both ends (VERY expensive). I know of systems that are a fraction of the size you have mentioned and the liverock has cost them well over $100,000 and this was for transportation that didnt include airfreight as the tank was in the same country!
Most public aquariums dont even use liverock in their largest displays. This doesnt mean that it isnt the best filter for the job (cos it is) but the cost would simply put them out of business. Most will operate mechanical filtration, deeper sand beds etc. The skimmers for a tank this sixe would be astronimical.. i have an 8ft skimmer that is for a small public aquarium and this little beauty costs about £5000 brand new!!! Its regualted for about 1000 gallons so you will need 50 of them at this size. (I cant get mine into the house though cos its too large
) ).
The we need to talk about flow. Ok a shark tank needs flow, good flow so the sharks can breath. No normal powrhead will achieve this and i would not like to even estimate the cost for this.
Then you need the alternative to the liverock as far as filtration is concerned. This would be mechanical.. probably a wet dry system somewhere else in the house etc. 50,000 gallons... i would aim for 5,000 for filtration and this is just a figure plucked out of the top of my head, i certainly wouldnt feel happier with a smaller volume of water taking the majority of the filtation on a 50,000 gallon system. I might even look for 10,000 to give me a 20% volume of filtration and a 10,000 gallon wetdry tank is collosal!
Then we need to aquascape. Unless you simply want a bare tank with sand for the sharks (which is ossible i guess) then some form of rock will be needed. Liverock is expensive as already mentioned so the alternative is ocean rock or something similar. It wont act as a filter of course but will give good effects on the eyes. However we then hit the same problem as before. You will need a special grade of size and as this rock is by far heavier than liverock, what you save on the rock in terms of costs will double if not treble the costs of shipping due to its size.. oh and yes you will definately need a crane to place these into position.
Lastly, a tank of this size usually doesnt have glass/acrylic on all sides, its made of concrete and only the viewing side is clear. This of course cuts down on costs but also makes the tank stronger. Having several tons of oceanrock/liverock on your glass/acrylic would terrify me no matter how thick it was. should one of these rock fall over then you will have a damaged tank there is no question.
This is a 17,000 ltr system.
Its a display tank and i have visited this place in person. Its a stunning tank but obvioulsy its tiny compared to the one you want to create. Whilst this tank is a thing of beauty I can also tell you that this tanks running costs are £800 (about $1,300??) per quarter!!!
This includes 12x 400w halides (which granted you wont need because your tank wont be a reef) but the sheer amount of electricity to run the powerheads and return pumps alone costs a fortune!
A 1200 gallon system
A 3000 gallon system
This is now in the area of using larger liverock for its visual effects.
The larger tank costs somewhere in the region of $150,000 to create so I am told
