Thank you everybody for pitching in (and kind words).
Billy, let me give you my 2 cents worth:
To make this a fair comparison, let's ignore the scales. Basically any scale that you can use with a Chinese DRO, you can use with TouchDRO. A more sensible comparison is between the DRO console itself and TouchDRO + a tablet. A Chinese DRO you can find for about $60 on eBay these days; around $100 if you get it from USA-based supplier with some semblance of support. TouchDRO will cost you about $250-$300 if you buy the adapter from me and get a name brand tablet. For the price you get:
1. Quality - TouchDRO adapter for glass scales is built as an industrial unit (ISO9000 factory, IPC Class 2 assembly, industrial grade components, no electrolytic caps, and solder alloy that won't crack from vibration). You can't get that with any Chinese DRO at any price point as far as I know
2. Performance - most Chinese DROs use electronics that were cutting edge in early 1980's. The $100 units are basically running the same chip as Arduino mega. It works OK unless you move the apron too fast or have fast power feed; it will miss pulses otherwise and over time accumulate error that you won't notice unless you are looking for it. The processor I use in the current generation TouchDRO adapters has hardware encoders. On
my site I list max pulse rate of 250KHz (around 250mm/second with 1-micron scale; in theory it can go to about 32MHz, but I don't have a way to measure this, so trying to be conservative.
3. Functionality - Chinese DROs are perfectly adequate when your work style is "zero out the axis, move by 2", drill a hole, zero out the axis ...". More complex things are pretty clunky due to low-fidelity display. If you work with sub-datum memory, tool offset memory, want to quickly indicate a part, etc. graphical user interface is factors of magnitude easier to use. On top of that, you get a completely new way to work in the graphical projection view that shows you the sub-datum coordinates visually, will select the closest one when you move the spindle (hands-free), lets you change cutter radius compensation direction with one click (and shows the relative cutter size and direction visually)
4. Support - I don't have "warranty policy". If you purchase a unit from me, I will take care of you, period, regardless of how long ago you got it. It it's something you broke, I can most likely fix the board. If it's my fault, I will make it right. This week I had a customer who bought a board in early 2021 and one of the inputs failed. I dropped off his replacement (upgraded) unit at USPS yesterday. Try getting any support from an eBay seller after the 30-day buyer protection period runs out (or, for that matter, during the 30 days period as well). I get emails daily asking if I can help figure out scale pinout because the seller can't provide the most basic documentation for the thing they sell.
Those are the objective measures (tell me if I'm wrong. I'm obviously biased here...).
A much less quantifiable, but I think very important, is the fact that I built TouchDRO based on feedback from the community. I'm a "paying sponsor" here specifically so I can have a place to bounce ideas off other hobby machinists. There are many features that were added based on someone's suggestion or idea. For example, idea for support for touch probe came from a forum member here, and in a thread right below this I'm chatting with a forum member about some ideas to make lathe mode more capable.
Finally, only about 1% of TouchDROs in the wild use hardware they purchased from me. I make the software, firmware and circuit design available for free, so the other 99% just build their units from commonly available parts. Latest version can be built for about $25 from scratch, or $50 from a DIY kit. Add $50 for a basic tablet, and you are in the price range of a cheap Chinese DRO.
Hope this makes sense
Yuriy
(is joke , no offense meant)