I'm not sure what's going on with Interactive Brokers (demo) P&L spread chart for a simple iron condor. I'm comparing it against market chameleon. IB TWS P&L spread chart is completely bellow the zero line and MC looks as expected. The example is for SNOW 320/325/460/470 (Jan08'21 expire) see attached:
The price between the two platforms seems just a bittttt different. (Quoting Bob Ueker there.) TWS is looking at quite a different animal.