I would suspect that Mr. Bishop's videos allow him some latitude on the production quality. He's teaching unique, long underground items from what I know (and own). There is a market for items like that, however, if you're pitching a DVD you hope to sell a lot of, you'll need far more than Mr. Bishop mentions. You'll need multiple camera angles, VERY good lighting and the last thing you'll want to do it burn them one at a time on a DVD burner.
As someone who's been involved in the process of releasing unique DVD's, you'll quickly start getting phone calls or emails from people who can't get your disc to play in their player.
Having a professional replicate them is the only way to go, in my opinion.
I had a conversation with someone about 6 or 7 years ago about a video tape they had released. It had sold 1000's and 1000's of them over a couple of years. It was a very successful video tape. He said he made $2.00 off each DVD (he sold them to a distributor). For all the hard work he did, all the traveling around and pitching his product, all he ended up with was a few thousand dollars from both projects, which took two years to release.
So, if you're willing to work your tail off for a few thousand dollars per year per DVD, you might be able to make some money, but I seriously doubt you'll ever get rich from magic DVD's.
There's a big player in the market who buys the rights to material and puts them on DVD. The conversations I have been involved in seem to be offering magicians anywhere from $2000-$10000 per DVD, depending on who you are and what you plan to teach. That's a one time upfront payout that will bring you no future revenue from that project.
I'm far from an expert on the subject, but I have been involved in a few deals and have been involved in releasing products a few times now.