Recently booked with Vayama for a well priced sale fare. Received an email stating that my booking was verified, and once my credit card had been authorised, my tickets would be issued.
Two days later I received an email stating that Vayama did not wish to offer the original fare anymore, and that I would have to accept their new (higher) fare.
Appreciate that air fares do change often, and that this time my tickets had not officially been issued. But I think it's a little odd to change the fare after several days and completing the payment / check out process. So, just a warning that Vayama may take some time to confirm your fares, and by that time it might be too late.