My translation agency recently raised minimum charges for small translations. We have also started applying a volume-based pricing scale with much higher per word rates for small translations.
This was due to the discovery that we were actually losing quite a lot of money on small translation projects, where our administrative costs were similar to those for large projects but the invoice totals were much lower.
For example, let's say that a client sent us a translation of only 100 words. If we charged on a per word basis, this would amount to just pocket change.
However, depending on the topic and the language, a project manager might spend several hours recruiting the right translator and editor and coordinating the project.
Then, we would have to prepare an invoice... and chase that invoice, which in many cases requires several e-mail exchanges with the client. We would have to pay the translator and editor. Both receiving and sending payment require staff time and, depending on the situation, involve transaction charges from the bank.
All of this without taking into account that many of our translators and editors charge us minimum fees for small projects.
So, from an agency perspective, a volume-based pricing system makes a lot of sense.