I don't know about "too good": I'm with Andy in seeing it as a risk.
I know nothing about this company, but cloud storage companies have gone bust or ceased operation before now, in which case the best you can hope for is that they'll give enough notice that you can download your stuff before it's lost. I'll guarantee their T&C's accept no responsibility on their part if the data are lost. But that's not a comment on them, it applies to any cloud storage company: use them for convenience if you like, but if it's important always have a backup of your own too.
So realistically I would not assume that this is 10TB "for life". I think the realistic question to ask is how much storage for how long would you need to justify the $100 cost, and then make a judgement about how likely you are to get what you consider value for this.