Declining prices mean that on a per-Gbit/sec, per-port basis, 10GBase-T requires less of an investment than 1000Base-T.
A CommScope Blog post from Frank Yang tells of the "dramatically declining" cost to users of implementing 10GBase-T. Yang, a technical marketing manager for CommScope's enterprise data center business unit, explains, "The per-port costs of NIC and switch have declined 87 percent and 70 percent respectively since 2007." The chart that appears at the bottom of this screen is taken from Yang's blog post. In the chart, the price points on the left side are per-port NIC list prices and the price points on the right are per-port switch list prices. Per-port NIC prices are charted by the brown squares and per-port switch prices are charted by the blue diamonds.
Yang also points out that the per-Gbit/sec, per-port cost of 10GBase-T is "approximately 60 percent lower" than that of 1000Base-T. In that respect, it is less costly to invest in 10GBase-T than in 1GBase-T on a per-Gbit/sec, per-port basis, he says.