Why I would want to be able to test on the simulator is clearly stated in my previous post.
It is also blatant that you are offering that on the Android side.
It depends on the fact that the Android apk can be run both on physical devices and the emulator.
This helps developers to try for different form factors and OS versions.
On the iOS side the XCode development encompasses two different kind of compilations.
You implemented just one of them on your server. The most common is not implemented.
XCode developers can do both on their Macs, so it is not difficult for you to provide that possibility, maybe changing just a line of a script.
Builds have different costs in terms of "credits" in your system, so each iOS simulator build would be 8 credit like the iOS build.
I think you would even have a boost in iOS builds with that option.
If you want to charge more you could include that in the "basic" subscription.
I have a free account because I did not need any of your advanced functions,
but I think that would be a reason I could subscribe, at least for a month.
It would be interesting to hear from other developers here.
Regards