Discrepancy between estimated cost for the run compared to when manually summing up the cost of all tasks

[pbieberstein2]

When exporting the analyzer statistics, from my understanding, the first row gives the stats about the entire run. For the column "estimatedUSD" the number for the run (in my case 81 USD) is very different from when I manually add up the costs for each of the tasks (130 USD). Manually summing up seems to match closely to the cost that I'm actually billed so what does that column actually mean for the first row? To me it sounds like those two numbers should match.

Thanks!

Philipp