It depends on your financial situation in life. Instead of thinking "expensive" versus "cheap" -- because they're just words with no clear definition -- you need to think about the cost for what you are getting.

$125/year is just over $10/month. Nowadays in the US/UK/Canada, that's about 2 cups of coffee at Starbucks.

For that price, you are receiving 1TB of backup space for yourself.

Each person is $10/month, which is useful if you need to collaborate and not worry about setup.

Insurance on your home always varies, but usually runs about $50-100 per month. And that's just the price you pay for when things are going well.

For me, there's a cost to peace of mind and the ability for me to save time in my life to do things other than maintenance.

FWIW, I look at Dropbox as a monthly insurance premium to ensure that my files will always be around and I don't need to worry that my in-home RAID server must blow up at any time.

How did you arrive at $125/user? A link for the unaware?