Do I Pull the Trigger?

I'll probably ponder this idea for another hour. 

Tim, my cubicle neighbor, told me that Best Buy has their 10 TB EHDs on sale for $159. I looked online and the Coralville store has 1 (ONE!) left! I am hesitating only because I still don't have a clear backup / replication strategy in place. I have 8427 duplicate files that I'm about to clean up. It's really tempting to just pull the trigger and get it.

The rational / logical side of me thinks about whether I really need two 10 TB EHDs within my collection of EHDs. In the following list, all numbers represent the TB capacity for that EHD:

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B       4
D/H   + 10
E     + 8
G     + 4
I     + 4
J     + 4
K     + 4
M/N   + 4
T     + 8
U     + 2
V/W/X + 1
Y     + 4 

       57

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The question I have to answer is: if I already have 57 TB capacity, why do I need 67 TB?!? Add into the equation that I have a Dropbox account (~$10 / month) and I have a BackBlaze account (~$99 / year) continuously backing up my file also backing up my files. Are my files that important?!?