Far fewer phone calls, or 'text messages'. A bunch of web-browsing and e-mail reading/sending (which billed at 'per packet' rates close to that of text messaging). One web-page, with graphics, could be *expensive*.
When the 'home plan' lets you do it _to_ any place in the world, it is *not* "all that unreasonable" to assume that the costs _from_ somewhere else in the world ("to home") will be of the same order of magnitude. It's the _same_ collection of resources being used, just in the reverse direction.
The assumption may not be _correct_, but is it *not* unreasonable to expect things to be 'of the same order of magnitude'.
They aren't.
But the conclusion _does_ hold a fair degree of validity, regardless. :)