I purchased an inexpensive 50Ω dummy load rated at 25W from Becen on Aliexpress (~$20 inc shipping), the intended application is HF.
Above, the dummy load.
Above, the centre pin passes a gauge test, doesn't satisfy the Precision N criteria, but well within tolerance of non-precision N connectors.
RF performance
Above, the VSWR plot from 1 to 101MHz.
Above, the ReturnLoss plot from 1 to 101MHz. ReturnLoss is a better metric for low VSWR loads. ReturnLoss is better than 30dB from 1 to 101MHz.
RF performance is very good, especially for an inexpensive load.
Thermal performance
Above is a thermograph of the load dissipating 12W for 10m, temperature rise is 55°. This is really the limit of continuous power rating, and even then, at 20° ambient, the heatsink is hot enough to burn skin.
Like most power rating claims, they are a lie.
Nevertheless it is a good 10W continuous rated load.