I don't know. $10 a month really doesn't seem like a lot of money to me. Especially considering the cost of, say, the computers you're running it on.
But if you really say want 5 gigs, then $10 a month seems a bit high, especially now that Gdrive gives you 5 gigs free.
Its also a bit of a pyschological barrier seeing that second digit in the monthly bill as opposed to say $5/month and knowing that the yearly cost breaches the triple digit barrier.
Realistically though, I totally agree.