There are more things than price that can prevent competition from reappearing once it became extinguished. If there is a constant threat of the prices being l

There are more things than price that can prevent competition from reappearing once it became extinguished. If there is a constant threat of the prices being lowered again, it will be pointless to reinvest in restarting competition - the monopolist at any time can lower the prices back down. Also, in some fields the monopolistic position gives network effects to the producer that cannot be replicated by an upstart, making a competition unlikely.