小三不是3块钱
[xiăo sān bù shì 3 kuài qián]
'Xiaosan (a third party/cheating partner) does not cost 3 yuan' suggests dissatisfaction with being devalued. Xiaosan colloquially refers to an affair relationship, whereas this statement implies that being someone's lover is worth much more than such a trifling amount. It carries connotations of both protest against and defiance of such evaluations.