Everything is worth what you'd personally pay for it. If you feel you'll get value for money, then who is anyone else to tell you that it's too expensive?

Oh and it's ridiculous to suggest that mobile phones are unnecessary these days. If they were, then why is IT seeing such a channel shift from traditional to cloud? People want to be able to work on the go, and on mobile devices, which is why the service industry is adopting to that channel shift. Having the likes of your mail, Lync, Office on a device is an absolute life saver! I can quickly fire off responses to mails whilst travelling, without having to lug a laptop around everywhere.