rack rent 22:24 Feb 12, 2014
According to Oxford Dictionaries (online), rack rent = an extortionate or very high rent.
examples of usage:
'They were a subdued and powerless people owing their very existence to landlords and their agents who worked them to the bond with rack rents.'
'A rack rent, therefore, was a high, level rent, unlike earlier forms (mainly beneficial leases and copyholds) that had the tenant pay a large lump sum followed by a nominal rent and, perhaps, feudal services in money, labor or kind.'
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Merriam-Webster's Unabridged Dictionary defines 'rack rent' as:
'1: an excessive or unreasonably high rent
2: British: the highest rent that can be earned on a property' | 
peer agreement (net): +3