Digital TV convertor box price gouging

I received my $40 coupon so I headed to Walmart, where I had previously seen a pile of these boxes for $49.99. This would be after my $40 coupon discount I would only have to pay $9.99. Not a big deal. Upon arrival I find none, zero, zip. So I preceeded to ask the sales clerk about them and was told that they were out and not sure if and when they would get any more. So my next stop was Best Buy to find 4 left on the shelf. Their price was $59.99! So after my $40 coupon discount I paid $19.99. Now is this price gouging? I have emailed the governments website for this but have yet to hear back.