The Wellcome Trust recently made data available on articles which have been made open access during 2012-13 due to APCs paid by Wellcome-funded authors. This data has since been cleaned up, improved upon, and augmented by a number of people working together (see these posts from the Open Knowledge Foundation for a summary of this work so far, and a follow-up post from the Wellcome Trust).
I’ve taken the 1677 articles which have so far been marked with the Impact Factor of the journal that they were published in, and plotted them on a graph against the APC that was paid for each of these articles:
This gives a very rough idea of the fact that there may be a correlation between the level of APC levied by a publisher and the Impact Factor of the journal. Once the data is more complete we could create a new version of this graph and present it more clearly, adding a trend line.