As if a night a strip club isn’t expensive enough, we bring you a tale of woe for an ex-RBC (now Thomas Weisel) trader that is trying to recover the dough for a “promise” made to his ex-gf for what could be a very pricey boy’s night out. Apparently, boys won’t be boys…

The NYPost reports that Greg Calvino (45) is suing ex-gf Elisa Kwon (”thirty-something”) claiming extortion. At issue is an alleged $100,000 promise that Calvino made to his then girlfriend to not “use drugs, stay out late, frequent strippers or prostitutes.”

Calvino contends that he wrote the hefty check in response to Kwon’s attempt to blackmail him by bringing tales of drug use to his then employer, RBC. Calvino’s extravaganza allegedly took place in March of 2005. The NYPost reports that the couple, who dated for two years, broke up in April of 2006. Kwon cashed the check in November of 2005.

Kwon’s affidavit includes an alleged IM conversation between the two that with Calvino admitting “sorry I was irresponsible last night - but I didn’t do the bad stuff,” but then is confronted by Kwon who writes, “$25 Rite-Aid” test - “it’s POSITIVE.”

Calvino also writes in the alleged IM convo: “He put it in my face.”

What “it” is we can only guess.