The first is a real piece of work from back in the day(made in China) VA18B
The second a Masterrcraft Multimeter that I've owned for nearly 10 years that's been laying about my tool bin. Both of which appear to support the same level of square wave measurement capabilities as the first meters.
And so to date we have the following in order and/or age:
Mastercraft Multimeter - Model 52-0052-2 - $29.99 CA
V&A VA18B Digital Multimeter With USB Interface - $49.99 USD
Dawson DDM350 Pen Type Meter - $29.99 USD
Brymen BM869s PC Logging Multimeter - 300USD
I also have an old MASTECH Bench Top DMM that I might add to the sample pool as well, though the selector switch is broken on it, and so I'll have to look at repairing it first. Though I'm going to venture it will likely follow suite with the remainder of the pack in that these all appear capable of measuring square wave frequencies without issue.
That said, I'd say the prognosis appears quite good in that most anyone should be able to take a reading of their own zappers. Which should at the very least give them some ball-park figure of where things are at in terms of running frequency.
PS. based on the results, you might want to consider getting a better multimeter :p