which powerline adapter to get?

[luv2liv]

for whatever reason, my raspberry pi wifi auto shutdown. even with wifi power management off, it would stop. so im hoping a wired solution will eliminate this drop issue.

which do you suggest and why are they still so expensive??
here's a pair for $29.
http://www.amazon.com/TP-LINK-TL-PA4...sr_1_1?ie=UTF8

i see those mini usb wifi adapters dipped below $8. while the powerline adapters are virtually unchanged, still $14 per.