It isn't BPC that is lying, it is a few of the players adding duff info.
You can filter out the (obviously) incorrect profits + you need to be wary of any prices that haven't been updated for sometime.
Remember that any run you see with high profits can be seen by thousands of others - don't be surprised if prices are trashed by over trading by the time you get there.
Systems that are missing need to be added before they will show.
I haven't used EliteTradingTool but unless it it somehow ripping the raw data from ED, how it does it avoid the same issues?
[Edit - just tried out EliteTradingTool.co.uk: Although lacking some of the features available in BPC. it is very simple to use and extremely quick. However just like BPC, if commodities are either entered incorrectly or not updated at all, it suffers from exactly the same accuracy issues (on some commodities). I am looking at a simple 2 jump there and back route that I have been running for the last couple of days that is making avg cr/t 2100 and ETT is telling me I would make 1350 cr/t. This is because the prices haven't been updated for several months and to be completely fair BPC is only up to date now because I have been updating the prices while I run the route. I will update both tonight at the same time and then compare them once they have updated (at least I only have to OCR the stations once

)]
I use these tools to find areas where I think there may be profits to be made, but gather the data myself once I arrive (before wasting profits and more importantly time). At least if you have updated it, you know it is accurate. Otherwise you can never be 100% sure the data is accurate.
If the profit to be made looks unrealistically high - it is probably wrong (and might even be a Trader Trap for a pirate group).