£500k is actually not bad because she didn't go on her own don't forget and they're already paying Titan Airways to lease the aircraft anyway so it makes sense to use it.
She probably took a team of people and for 10-30 people in the government and civil service that would easily go to well over £100k.... This is all unless the UK government decided to travel on a foreign airline in economy which seems unlikely. With the expenses they all get I don't think even the hardest within Labour would stoop that low.
I'm not excusing anything, this is just an example of the kind of eyewatering money wasting that occurs with every government. It's why we're all paying for the mortgages on their second houses in London and beyond.