Estimating MQL5 Cloud Agent Costs

 
I like the feature of the MQL5 Cloud Network for assisting in optimization runs and I thought I would be able to approximate the run of my script by performing a small sample size run ~500 and then dividing the cost by the number of runs.

My initial calculation was $0.00026 per run and I extrapolated this to a larger run size to estimate what the cost would be.

Unfortunately the cost ended up being more than double the initial per unit run! 

Is there a more reliable way of estimating the cost of a run before you start as MQL5 Cloud Network doesn't seem to stop when you've run out of credits either?

I understand that the system uses PR and MB to cost, but can this not be provided to the user prior to submission to help calculate?