That's not extravagantly expensive! And the new Phonofone isn't as extravagantly designed as the earlier place-your-iPod-earbuds-in-a-special-listening-chamber version, either—just pop your iPhone 4 in the dock and the ceramic horn will amplify the audio coming out of your iPhone's speaker roughly 4 times, or about 60dB.
Just pop your iPhone in the dock and the ceramic horn will go about amplifying the audio from your iPhone's speaker to about four times the original level. The first batch is limited to fifty units only so if you're planning to give this out as a Christmas present, you'd best hurry.