The price for both platforms should be the same, at $4.99 USD. Other currencies might vary based on the conversion rates the sites are using, but ideally, they should be very similar.
Steam translates the price to other currencies differently than Itch does. I apologize for the discrepancy, but I don't know how I can alter foreign currencies on Itch to match the ones on Steam. For now, the prices will stand as they are to keep the USD price the same.