First, congratulations on picking up your 5.5 in the nick of time before the price spike (it would call it "recent", but as I've pointed out before, it actually started more than a year ago at this point).
Second, as to assertion about new raw copies coming to market every week, well let's check the census to see what the vast majority of those copies have looked like since 2000 (when CGC started). Out of about 2300 copies submitted, 750 are restored (about 27.5%). And out of about 1650 graded blue label copies, the average grade is 3.62.
Whatever else is left out there, odds are many are restored and most are very low grade (based on the sample size we have now).
This, of course, isn't taking into account all of the multiple CPR's that have been done with this book that are skewing the census artificially higher.
At the end of the day, this book us much rarer, even in decent mid grade condition, than many would have you believe, and I also believe the actual amount of decent, grade-able copies left in the wild is more myth than reality at this point (although I have no doubt there is certainly a palpable amount, but clearly not enough to negatively impact prices at this point, not even in low grade).
-J.