I've had several borescopes, the Lyman Digital, an Oasis Scientific, a Teslong, and have access to a Hawkeye optical borescope.I looked at those cheap Bore Scopes and saw few advantages. I purchased a Lyman Digital Bore scope that has many advantages over the cheap stuff. I can use it at the range on Battery Packs like I charge my cell phone. I can Capture to memory card and then transfer to my desk top. There's a scale on the probe, so I can tell exactly where any fouling or damage is located. Good clarity on monitor as well as my Desk monitor. Well worth the investment.
The Lyman was the first generation with only 320x240 resolution and the monitor was intermittent right out of the box, then the buttons on the monitor quit, Lyman replaced it, but the replacement had image quality issues, so I returned it and Lyman eventually refunded my money.
The Oasis Scientific is the GB-460 model with wifi connects to my iPhone, or iPad wifi with no problems or my Windoze 10 laptop or desktop using the Windoze Camera driver and captures images or video. Older versions of Windoze will need the free software from Oasis. The GB-460 can also be connected via USB. Mine was on sale for $199 with the wifi bundle when I purchased it.
I bought the Teslong because I needed a semi-flexible, small diameter borescope for some non-firearm related projects. I think it was $50 when I purchased it. It is strictly USB, but it plugs into the Oasis Scientific wifi adapter and works fine with it. Using the wifi adapter I capture images or video direct to my iPhone or Ipad. With the USB, I capture images and video directly to disk using the Windoze camera drivers.
The Hawkeye is better than the digital borescopes, but not $600 better and isn't flexible.
Lyman has a new 'Pro' version for $350, but like the earlier generations it uses proprietary parts, so your stuck with it and has no USB. It requires an app to work with iOS or Android, it also doesn't work with Windoze according to the Lyman website. It now has a 720p camera, same as the Oasis and Teslong.
For less than $50, the Teslong works very well and is more than adequate for any hobby shooter. Mine is 2 years old and has held up fine to some fairly heavy use in less that ideal conditions in dirty, oily, hot engines.
The Oasis works better as a gun barrel borescope than the flexible Teslong. Teslong also sells a rigid version that looks very similar to the Oasis for around $75. The wifi adapter requires an external USB power source, either a PC USB port or a USB power cell. The price for the borescope and wifi adapter is currently $249, but they regularly run sales or coupons.