The most cost-effective approach is usually:

1) Use one embedded wallet provider + one wallet connect library

Don’t build wallet UX from scratch. Pick:

• An embedded wallet provider for account creation / social login / key management
• WalletConnect for connecting to external wallets

This gives you:

• Embedded wallet for new users
• WalletConnect support for users who already have MetaMask/Rainbow/etc.
• Lower engineering cost and faster launch

2) Keep the auth flow simple

The cheapest production pattern is:

• Social login / email login
• Create an embedded wallet automatically
• Add a “Connect wallet” button using WalletConnect for external wallets
• Default to embedded wallet for app actions, and let users switch when needed

This avoids:

• Custom seed phrase handling
• Manual key storage logic
• Complex wallet-creation UI

3) Use a provider that supports both embedded wallets and WalletConnect natively

This is usually cheaper than stitching together separate auth, wallet, and signing layers.

Look for:

• SDK for embedded wallet creation
• Support for WalletConnect v2
• Session persistence
• Cross-device recovery
• Smart account / account abstraction support if you need gas sponsorship

4) Minimize on-chain signing complexity

If your app needs only a few signatures, keep it to:

• Login / create wallet
• Sign message
• Send transaction

Avoid adding:

• Custom transaction batching
• Multiple wallet switching states
• Complex multi-wallet routing logic

Every extra flow increases QA and support costs.

5) Prefer account abstraction if gas UX matters

If you want the cheapest good UX long-term:

• Use smart accounts / account abstraction
• Sponsor gas for users
• Let users use embedded wallet or WalletConnect-connected wallets as a signer

This can reduce drop-off and support tickets, even if infra costs are slightly higher.

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Practical low-cost architecture

Option A: Lowest engineering cost

• Embedded wallet provider SDK
• WalletConnect v2
• One app session store
• Embedded wallet as default signer

Best for:

• Consumer apps
• Quick MVPs
• Teams without wallet infra experience

Option B: Lowest vendor cost

• Build more of the auth yourself
• Use WalletConnect directly
• Manage embedded keys internally

This is usually not the cheapest overall unless you have a strong blockchain/security team, because implementation and audit cost go up fast.

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What to avoid

To stay cost-effective, avoid:

• Building your own key management
• Supporting multiple wallet SDKs early
• Overengineering recovery flows
• Supporting every chain and wallet type at launch
• Custom wallet modal logic unless absolutely necessary

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Rule of thumb

If your goal is cost-effective embedded wallet flows with wallet connect integration, the best path is:

Use a hosted embedded wallet provider + WalletConnect v2 + simple login + minimal signing flows.

That gives you the best mix of:

• Low development cost
• Fast time to market
• Reasonable security
• Good user experience

If you want, I can also compare specific stacks like Privy vs Dynamic vs Web3Auth vs Magic vs Turnkey for cost and implementation effort.