These two solutions seem comparable to me. I still don't understand why adding Ethernet to an Arduino costs more than the Arduino on its own. I appreciate costs go down with volumes but an Ethernet shield is still at the top end of shield prices.
The schematics and circuit board design are available, at no cost. The list of parts used is available, at no cost. If you think you can source all the parts, and assemble your own board cheaper, go right ahead.