The promised blessings are conditioned upon obedience and turn into terrible curses upon disobedience:
However, if you do not obey the LORD your God and do not carefully follow all his commands and decrees I am giving you today, all these curses will come upon you and overtake you... (Deuteronomy 28:15)
What disobedience was there that wasn’t paid for?
“The promised blessings are conditioned upon obedience”
Tou are confusing the Mt. Sinai convenant (which is conditional, as you correctly point out) with the convenant with Abraham (which is unconditional).