This ...
"we are pushing our resources to 100% usage while running cronjob, they
are kindly asking us to upgrade to a higher tier or stop pushing it"
sounds like shared hosting. 
Their 'higher tier' would be a dedicated VPS with specs for spec/memory/cpu's etc.? Fun and games ... they xfer your shared hosting environment into a jailed (but dedicated) environment and then one has to figure out the jails.
What?!!!?? No virtual prize? ;)
'SoS', Ken