The cost depends on the memory assigned and the execution time.
AWS Calculator can help with your cost estimations. https://calculator.aws/#/addService/Lambda
Increasing the account's concurrency limit as no direct impact on pricing. With Lambda you only pay for what you use. If we increase the limit and you do not use it, there is no increase in cost.
Saying that, when you increase the limit, you risk having some bad situations when a function goes wild and consumes all the available concurrency, which then might have a cost impact.
The lambda pricing page https://aws.amazon.com/lambda/pricing/ has details on pricing for Provisioned Concurrency, under the "Provisioned Concurrency Pricing" section, should you choose to use Provisioned Concurrency. Other than that, the lambda pricing depends on memory assigned and execution time, as Carlos has mentioned above.
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