How much money was the last bet?

His final bet was 400 000$ and there are two ways to look into it.

First it is not said in the movie or written in script how much he bet at the final scene on Roulette. But we can see from the picture the amount of money, bills and currency straps placed on Roulette table.

These are common movie prop-money. Yellow currency straps represents stacks of 10 000$ of 100$ bills. The other currency straps seems to be more brownish (50% bill) than red (5$ bill) strap. Also the back of brownish strap bill seems to be more of 50$ than 5$ bill, so the stack represents 5000$. We can see that there are 38 yellow currency straps and 4 brown straps - that totals to 400 000$.

From movie perspective we can calculate his final bet by working his debt and bets backwards. His full debt before the final bet was 636 000$. He owed to Frank 286 000$ (260 000 + 10% per week)? and to Mister Lee 350 000$. Now the problem is, that we do not know what was the exact bet at Roulette wheel, because we do not know how much he won from betting at Lamar´s game?. But we learn at the end of movie that Frank offered Jim 100 000$ that was "little extra on the top for him", that Jim declined?.

We know that Roulette (red or black) bet ratio is 2:1 and all Jim´s loans were paid off with at least 100 000$ on top (736 000$), the initial bet must have been at least 368 000$ to achieve it. It is never said in the movie if Mister Lee also took interest on money, but it would be wrong to assume that he would loan it for free. So from calculations I would assume either the remaining 64 000$ (800 000$ - 736 000$) was interest or "little extra" for Mister Lee.

? When he first approached Frank it was stated that rate is 10% per week.

? He paid lamar 150 000$ (second loan from Mister Lee) for throwing a game by not winning more than 8 points. 260 000$ (loan from Frank) was betted at Lamars game by Jim, but we did not learn how much he actually won.

? The 100 000$ extra money, that Jim leaves for Mister Lee and Frank on Roulette table may not be intentional, because previous to final bet he offered 50 000$ to Dexter for making a trip to Vegas and placing a bet on Lamar's game, but Dexter declined it.