Not even my friends believe me when I say how much we spent building our ultra basic bellytank. When I tell strangers who ask that they'll want at least 50 grand they either think I'm pulling their chain,or an idiot. We built ours in a garage with primitive tools and spent money earned in wages. If you own a business and have employees the apparent cost may be low,but the inferred cost will be substantial.
Personally I'd be surprised if any of those top end liners cost less than a half a mil'.
Waaaaaay outa my league....
Edit: ...and I bet some have cost three,four or five times that,to build.