Vanity presses have indeed existed for a long time, but 50 years ago they were widely seen as a scam, rather than a realistic route to a writing career.

Vanity publishers would tell every author their work had great sales potential, then charge them $2000 for $500 worth of editing, printing and marketing - so authors would not only fail to make money, they would actually make a large loss.

And they would generally sell the authors hundreds of copies of their printed book (because it wasn't economically feasible to do print-on-demand like today), which the author was expected to find buyers for. Most didn't, and many people clearing out the houses of dead relatives found dusty boxes of unsold books which cost the relative a lot of money.

I don't think that's a huge difference. It will still cost you money to get your Word doc into publishable shape (cover and interior design, editing, etc.) And you're still unlikely to make a significant profit on that upfront cost as a self-published author of PoD or eBooks.

As to whether either form of self-publishing 'scam' or not, that depends on the expectations of the author. I think it's always been common to publish just to be published with no expectation of making money, hence the 'vanity'. But I have no data to back that up.

The difference is with print on demand you can actually control your losses. When print was a printing press, the effort to setup the press meant that nobody sane would print just one book, it cost a few thousand to setup to print, and then each book was a few pennies. Inflation has raised the latter cost, while print on demand as lowered the previous to near zero.

Today you can decide how much your editor is worth. If your grammar and spelling is good you can pay less, or if you know it is bad (like me) you can pay extra until the quality is where you want it. You might even have a friend who will do the early editing for free (a trained editor shouldn't be wasted on spell check duties, but they are probably worth it once you think the book is done for final tweaks) Whatever this investment is, you can limit the costs.

"Vanity Press" means you spend money to get published. Modern self-publishing means that you're attempting to make an income, however meager, from your writing.