Solidity Contract Deployment fails - but account has plenty of ETH

Question

I was just trying to deploy a new contract on the Ethereum MAIN-Net (not Ropsten, Rinkeby or the other test-nets) - and I’m getting this strange error:

Message:  sender doesn't have enough funds to send tx.
The upfront cost is: 159840000000000000 and the sender's account
only has: 158236521250000000

The reason I’m finding this strange is cause while I do indeed have only 0.158 ETH in my account - about $21.60 using today’s rate, which of course isn’t much, those funds should still be plenty enough for simple contract deployments. Especially considering the following:

-I deployed this very same contract - successfully - to:

1. My local Development Network (Ganache) - where the Total Cost came back at 0.01332576 ETH (about $1.80)
2. The Rospten Network - where Total Cost came back at 0.01342176 ETH - about $1.83

While I know there's obviously going to be a difference between the various test-nets and the REAL Ethereum Blockchain, it can’t really be like $2 on one and more than $21 on the other, can it? That’s like 1,050% higher.

Is there some other thing going on here that I'm not aware of?

Would really appreciate any insights into what's causing this.

=================================

UPDATE:

As per @smarx suggestion, I'm adding some code & context:

TOOLS:
-I'm using Truffle to deploy my contracts.
-Running ganache locally on my MacBookPro
-Running Truffle Version returns:

Truffle v5.0.4 (core: 5.0.4)<br/>
Solidity v0.5.0 (solc-js)<br/>
Node v11.10.0<br/>

Here's my deploying code - my truffle.json file.

require('dotenv').config();
const HDWalletProvider = require('truffle-hdwallet-provider');


module.exports = {
    networks: {
        mainnet: {
            provider: function () {
                return new HDWalletProvider(
                    process.env.PRODUCTION_MNENOMIC,
                    "https://mainnet.infura.io/vs/${process.env.INFURA_API_KEY}",
                    15
                )
            },
            from: "0xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
            network_id: 1,
            gas: 7992000,
            gasPrice: 20000000000,
            confirmations: 2
        },
        ropsten: {
            provider: function () {
                return new HDWalletProvider(
                    process.env.DEV_MNENOMIC,
                    "https://ropsten.infura.io/${process.env.INFURA_API_KEY}"
                )
            },
            network_id: 3,
            gas: 8000000,
            gasPrice: 20000000000
        },

        development: {
            host: "127.0.0.1",
            port: 8545,
            network_id: "*" // Match any network id
        },
    },
    solc: {
        optimizer: {
            enabled: true,
            runs: 200
        }
    }
}

As mentioned before, this code worked perfectly on both my local Ganache deployment as well as my remote Ropsten deployment. I also used this exact same code successfully in the past - as in last week - to deploy contracts to mainnet, so I know it has worked and is good for at least some deployments - and I thought it'd be for all of them.

Hope this sheds a lot of light. If more info is needed, please let me know specifics.

======================

UPDATE#2 - thought I'd throw in the exact copy of the error truffle is giving me:

1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------
Error:  *** Deployment Failed ***

"Migrations" could not deploy due to insufficient funds
   * Account:  0xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   * Balance:  158236521250000000 wei
   * Message:  sender doesn't have enough funds to send tx. The upfront cost is: 159840000000000000 and the sender's account only has: 158236521250000000
   * Try:
      + Using an adequately funded account
      + If you are using a local Geth node, verify that your node is synced.

    at /usr/local/lib/node_modules/truffle/build/webpack:/packages/truffle-deployer/src/deployment.js:364:1
    at processTicksAndRejections (internal/process/next_tick.js:81:5)
Truffle v5.0.4 (core: 5.0.4)
Node v11.10.0

Answer 1

The values in your config for mainnet are 7992000 gas limit and 20000000000 gas price, which leaves a tx price of 0.15984 ETH, which your account doesn't have enough for. A tx with a gasPrice*gasLimit+value higher than the accounts balance can't be mined, as it wouldn't have a high enough balance. Try lowering the gas limit to 7000000.