Check the documentation on Commitments. It is 10k.
Still, you wouldn't deploy more rollups to scale your dapp.
A "smart rollup" is a blockchain primitive like a smart contract, not actual infrastructure. Your job would mostly be focused on scaling the underlying infrastructure and making sure the whole deployment works effectively.
The throughput and TPS is then dependent on the infrastructure decisions and design that you make, and the storage limitations of the underlying L1. You can scale infrastructure independently without making new sr1 rollup addresses.
The smart rollup is your actual business logic that gives some output based on a series of inputs. This is data stored on the blockchain.
The rollup node is software that reads the Tezos blockchain, finds the L2 messages, then sends them as a series of inputs to your business logic, and come up with a resulting commitment. It costs 10k bond to post this resulting commitment to main L1 chain.
The infrastructure is whatever you come up with to run the rollup node software. Scale it horizontal or vertical. There are still L1 limits so you cannot scale infinitely. (Data Sharding is the future solution)
The 10k bond is more about ensuring that the commitment you post isn't a lie. If it is, someone else can stake 10k and post the correct commitment and slash your bond.