Heh, if only. Just a sheet of 48x24x1/4in acrylic at Home Depot runs $65 ...and for this project you'd need three! Then there's the labor. How long would you guess it takes to precision glue (to within, say, 0.5mm tolerance) a couple hundred pieces?
Still don't believe me? See what this guy went through for a similar project, except uncovered:
http://thehomescientist.blogspot.com/2013/02/the-element-display-introduction.html
But yeah, if there was a machine that could pop these out they'd be dirt cheap.
I thought of the contacts idea for the gases. It might be doable but hydrogen and helium would quickly leak out. Plus the idea here is to provide a set that the collector can fill rather than provide a partially filled in one.