I find this data fascinating - partly because I don't understand it. I regularly send bitcoin and, as far as I can tell, have never spent more than a tiny (unquantifiable in fiat, as in much less than a cent) amount on transaction fees. Can anyone more savvy chime in on the discontinuity here?

Not an expert, but I did make my own erc20 once.

Are you sending it over the network, or to someone else within a website? (eg: binance, coinbase; doesn't need to be an exchange)

Do you track your transactions later? Do they get confirmed? How many confirmations does a website need to count it? How long does that take?

I would expect a low-fee transaction to eventually either expire or go through. I don't know what timeframe that might take: higher fee typically means higher priority as I've understood it. I can't imagine it'd keep your $ in limbo forever, but who knows. If you haven't used it in a long time, I understand that the network is much more congested these days.