Take a look at https://www.stellar.org/faq/#_What_are_the_fees_for_a_transa.... The short answer is that each transaction burns 10 microstellar, and they haven't smoothed out all of the display issues in the hosted client yet, hence the surprise.

The cost of transaction might be an issue if one day 1 stellar > 20 USD or so (it becomes too expensive). Wondering if there is a way to fix it (other than simply merging multiple transactions), without having anything to do with the USD itself.