I thought I had more pics of the rust bubbles but I can't find them right off hand but here's one I took to compare to what you have. This was the worst rust area I had (driver side, the first pic from my previous post and the area my buddy is working on in the second pic).
If I had to guess, I had 3-4 hours in making patches, and then we had another 10-12 hours in cutting out rust, making the patches I missed (mostly inner structure panels), welding it all back together, doing the rough body work, and covering it in 4 coats of surfacer. This is not yet ready to paint as it will need some more body work for that. However by the time you paint it you can have 20-30 hours wrapped up in it pretty easy and at $50-$100 an hour plus materials you're up into the 4 figures pretty quick. This is why most guys opt for just buying a new bed.
I went this route because I already had all of the supplies and tools and the knowledge I didn't have my friend did (he's a professional hot rod builder, I pay him by the hour anytime he works on my projects). I went this route because at least I know we got as much of the rust as we could. A different bed would have just been a gamble. There is foam between the inner/outer body panels and is a guaranteed rust mess in this area of these trucks. Damn you Ford!