I bought one of these sauna tents and it was pretty underwhelming. I can barely stand 30 minutes in a real sauna - in this home sauna tent, I watched an entire movie (two hours) and had to get out more from boredom than the heat.
Clearly I'm trading low quality/cheaper for more time in sauna, since it does take more time to heat you up. I put a towel around the neck hole to accumulate heat, but I'm dripping with sweat in 25 minutes. I may not be Finnish, but the model I'm using really does get me going.