I was out of reach for internet for a few days, hence the late reply on my own thread.
If all would have failed, I would have been ready to accept the $269 as a fee for my stupidity. And yes, they warned me several times, but I had them in my scedule when to pay and that somehow got messed up. Like I said, my stupidity combined with some events outside our control.
Wathever, I emailed that registrar and told that as non-profit, we did not have those amounts laying around, etc etc. Not a sob story but admitting we were wrong but unforseen events played a role as well.
To make a long story short, they lowered the fee to $ 130, including renewal, which we tried to pay immidiately. Then three credit cards of my US non-profit colleagues were blocked by their banks "because the secure payment page belongs to a foreign company". That this is a major player does not matter; as part of their anti-fraud efforts, those banks block all online payments to foreign accounts.
I finally managed from my side with a Czech credit card, and the payment was accepted by the domain registrar friday night. Now we am waiting that the site goes back up in the air. For once, a happy end and a lucky escape from what could have been wordse.
Thanks for all comments