FWIW, Lance buys the machines himself using his patron funds and doesn't let manufacturers into his process. Most don't even know they're being reviewed unless he has issues or specific questions he can't get the answers to elsewhere. He's frankly more qualified to test and compare such features than nearly anyone else, since he has thousands of hours of stick time with hundreds of machines at this point.
To get back to the bulk of your question, in many other industries where water heating is done, there's cheap thermoblocks and good thermoblocks.
Double boilers have been around long enough that improvements today are incremental at best. Heat Exchangers and Thermoblocks on the other hand seem to be improving by leaps and bounds still, and Thermoblocks in particular are getting a lot of development in other industries.
It looks like Ascaso is using decent blocks and is properly PID controlling them. Obviously it's not going to be as stable as say a full brass double boiler, but the results seem to outperform most heat exchangers.
Value is tricky though. You're right, it's a crowded market at that price. Personally at this moment, given this review at face value I'd still go with a Silvia Pro X today. But I expect in a few more years heat blocks might be able to match performance with dual boilers for cheaper and with less work.