Of course the dimensions can be expanded. If you used 16' 2x4s for connecting the pallets, you would end up with a 4'x4'x16' piece of structure.

In my area it is easy to get non-treated pallets for free from construction sites or lumberyards. And sometimes cinderblocks can be found for free.

This cost effective structure could end up costing less than $5 for the person that has their eyes open for free stuff.