If you took that same time, and invested it in working at Target, or Amazon etc, would you have more or less money than it would cost to buy an off-the-shelf battery? There are obviously other pros and cons.

I think Target isn't the right comparison here - the skills required for this project are worth much more than minimum wage bagging groceries. If you assume something like $50 an hour (on the low end for a skilled electrician), you get to the $6800 number in the parent post pretty quickly.

Of the three options, DIY battery packs, premade 100aH battery packs, or white glove powerwall a minimum wage earner would likely not have the skills to DIY the battery packs nor the money to pay for the powerwall.

Battery packs are an efficient market commodity and that’s pretty hard to beat for value for money.

Once full installations become more of a commodity then DIY with premade packs becomes less worth it.

It all comes down to what makes you happy.