You absolutely correct about the costs of the standalone USB to serial devices available now.
I overstated things a bit. (I am a bit surprised that the standard FTDI cables still go for about $20 though)
I was mainly comparing the costs of using a USB based ISP programmer without
using a bootloader to using an "UNO" type board or one with with the USB to serial built in
which makes using a separate programmer more expensive than using a bootloader.
There are some great low cost USB to Serial boards out there. I've actually looked
at that one. While usable, it is unfortunate that they didn't use the FTDI pinout -
it would have made it a direct drop in for the Arduino crowd.
--- bill