Britney Spears will be raking in HUGE STACKS in Vegas this winter -- a ridiculous $310,000 per show ... nearly $15 million per year -- but she still doesn't hold a candle to Celine Dion.

TMZ is privy to the financial details of Britney's deal. The 2-year contract calls for 48 shows a year at Planet Hollywood. According to the contract, Britney will earn $310,000 per show.

By contrast, Celine does 70 shows a year. Sources say she pulls in $476,000 a show ... so she's way ahead of Britney in the money department, but Brit gets more time off.

Britney's cut of the gate is huge -- projected sales per show are $508,514, meaning Brit will be snagging more than 60%.

As we reported, producers are shooting for a "cool, hip club-like show" ... unlike the run-of-the-mill Vegas shows that preceded it (Celine's included). It starts in December.