Tanks dont have to be expensive, you just have to stay away from the package deals and make your own systems up.
My 200 gallon tank only cost £220 to have built , i have then spent another £50 on the covers and £300 on electrical equipment (filters, powerheads, lighting and heaters) and built the stand from timber pinched from work. So all in my 200 gallon tank cost me £570 for a top of the range sytem, which is only a little more expensive than a Juwel rio 400 which is half the size and has inferior equipment (mine has 3 eheim externals, twin visitherm 300w heaters and a solid timber stand compared to the juwels 1 internal filter, single 300w own brand heater and stand made from laminated chipboard).