Results from my 50 + 5 crates:
Over half of the crates dropped rentals, and I got less than 1 part per crate (excluding special crates). There are talks of how the very first few crates tend to have better drops than the rest, and this does look quite plausible here.
It's also amusing how I got 11 rentals in a row; a friend of mine got 9 rentals in a row in his 10-crate run, and that doesn't look encouraging for prospective spenders (if there are any). He got 99 parts at the end, and among them 60 parts are from special crates, including one that dropped 50 parts. Even then, he said he felt doubtful on buying crates because he doesn't know how many more rentals he would get from crates before getting the single part he wants.
Thanks for the anniversary event. Congrats to those who got the tank within 50 crates. For those who didn't get it, you're not alone. Business is business, I guess? But I will leave that for others to discuss.