I use a similar system as SD. I don't bring fresh food like steaks or frozen items, but I do bring cheeses and meat sticks that I want too keep cool.
I have a Granite Gear food pack, about $90. I got in on sale for about $50. I cut a piece of 1" close cell foam that fits the bottom of pack.
 I use the same Sterilite boxes, except for solo, I use 2 of them.
To make it a "insulated" box, I wrap a 1/2" Thermarest foam pad around the boxes. Either the 20" or 25" will do, depending on how hight the boxes stack? I then have a piece of close cell foam as a " lid".
 With this set-up, SD's freezer pack tips, I think you could get the same performance for a lot cheaper than $400.
 Foam and pad serve a dual purpose. The foam wrap, protects the boxes from rocks and wear and tear as you portage.They also "quiet" the food pack. The Thermarest pad will make a great seat on wet or cold ground. You can even put it under your sleeping pad for a little extra comfort if you are forced to use a less than ideal tent area. Last, but maybe not least, if you dump, your heavy food pack will float, no problem ;D
 You can buy the Thermarest pad, Sterilite boxes, and freezer bags for under $50, and the close cell foam you can often find in commercial packing boxes. You could buy the food pack, and save $150 on the extras too make it an insulated pack.