I have chosen more expensive flights for the more airline miles.
I have considered using miles to buy a flight, then expensing the full retail cost (I don't cause that's straight up fraud)
The "purchasing more expensive flights for more miles" I understand as being unethical....but I honestly don't see an issue with redeeming your own personal miles and getting compensated by the company.
If someone gave you a $10 gift card to McDonald's, and used that to buy your lunch for $10, should you not get reimbursed because someone gave you the gift card and it didn't 'cost' you anything out of your own pocket?
Nonsense! That $10 gift card was yours for personal use, and is equivalent to cash.
Likewise, if you accumulate 30,000 frequent flier miles - for personal use - and you are able to redeem those miles for a free flight to anywhere in the US, and you instead use them to purchase a business ticket that would have otherwise cost your company $500, I see no issues with asking to be reimbursed the cost of the ticket ($500) even though it cost you nothing out of pocket, because you deprived yourself the value of your own personal frequent flier miles ($500), and the company would have paid the exact same amount ($500) if you hadn't used your miles.
Granted, that's assuming that the $500 ticket was the cheapest one for that flight schedule that you would have bought anyway, even if you didn't have any miles to redeem.
This is hilarious because per diem dollars aren't any MORE valuable than your normal salary dollars. Why weren't they sleeping in their cars back home?
Probably because if you get, say, $100/day for hotel lodging per diem and instead stay in your car, that's $100/night, or $3,000/month.
First of all - if they had to sleep in their cars every night, they would still need places to get ready at every day, versus just a 1 or 2 night thing. Not to mention things like a tv, kitchen appliances, places to store your clothes, etc.
Also, their rent may have been, say, $1,200/month, or $40/day. If you can sleep in a car for 1 or 2 nights and bank $200 for something that doesn't really inconvenience you that much (it's not like you're giving up your permanent home back home), it's a hell of a lot different than being all-out homeless 24/7. If you know it's just for 1 or 2 nights, you can make do with a small travel bag...but living out of a car 24/7 is quite a bit different!