The forward is set to run down the final year of his contract at the Emirates Stadium but the Gunners boss insists the club will make the sacrifice.
Alexis is out of contract at the end of the Premier League season and the Chile international is no closer to signing a new deal as he reportedly eyes an exit.
The 28-year-old has been linked with Manchester City, Paris Saint-Germain and Bayern Munich.
Wenger, however, has no plans to sell Alexis, even as the former Barcelona forward’s contract winds down.
“It is a financial sacrifice. It is a sacrifice that you have to calculate how much it costs,” Wenger said of Alexis, who sat out the season-opening win over Leicester City and will miss Saturday’s match against Stoke City due to an abdominal strain.
“If you let the player go and you buy somebody you spend maybe more than you lose. And as well if you extend the contracts it costs you maybe more than you lose when you keep the player. So you have to consider the length of the contract as well that the players want.
“So all that is in consideration, the financial sacrifice is not as heavy as it looks.”
“It’s my decision, but after the board has to of course agree with me. And if they don’t agree we have to consider it as well, and I will accept it. But the board is behind me on that.
Wenger added: “You can have an estimation of what it costs if you lose the player, what it costs if you extend the player, and all that. What it costs if you buy a new player. You can do that, approximately. After that, the ratio between what the player will cost, what he brings back, this has gone.
“How can you quantify today what Neymar costs? Will he bring €300 million back? It’s impossible to say. There is a part that is rational, and the other part is completely irrational: it is passion, ego, pride, you can call that how you want. How much is that worth financially? Maybe that’s down to every club.”