Very competitive, high quality, and you will have no problems scaling with them. Tech support actually cares about your problems too. I have been a direct customer for well over a year (nearly two) and have numerous clients with accounts with them as well.
There are 3 plans to choose from with Flowroute.
You can get unlimited channels (concurrent calls) for about $1.50 per DID. You will pay 1.2c per minute inbound and .9c per minute outbound.
You can get two channels with unlimited inbound, .9c per minute outbound, for $6.50.
Virtual PRI channel. Each channel (a single call) will cost $17.50 and will have unlimited inbound, .9c per minute outbound. You can assign each DID individually to be part of your Virtual PRI group. This is very good if you are going to be doing high volume. You just need to purchase enough channels to cover your usage.
You mentioned 40 calls at the same time. You need to break that down into outbound and inbound calls. With a Virtual PRI outbound calls do not count against it. So you will only need to consider concurrent inbound calls.
Just run some calculations on your end and you can see if sticking with the 1.2c per minute is a better deal than going with the Virtual PRI.