That rebar bicycle is completely a joke. This isn't "low cost engineering" it's "bike nerds got ahold of a welder and some rebar".

Rebar of that diameter isn't even commonly available.

It's also unusable heavy, and a needless waste of valuable steel scrap.

Sell that several hundred hunk of rebar, and buy yourself a brand new bicycle.

Here is a guy that did one as a sculpture at his university: http://rebarbike.tumblr.com/