Do you have any data to support this? AFAIK most newer TVs support 24, 30 50 and 60 fps. But you might know something I don't.
I'd be very surprised if the core components in all TVs made in the last ten years are not capable of supporting 50Hz and 60Hz on an electrical level. 50Hz and 60Hz are throwbacks to when TV frame frequencies were regulated by the utility frequency (of AC) in the country they were used in but I can't believe any TV manufacturer hasn't moved to programmable PLLs nor is there any reason for the panel itself to be engineered to only operate at specific frequencies.
In the EU we've long had 60Hz support in our TVs but I suppose it's possible in the US that it costs more for FCC certification if you're including 50Hz as well. I don't know how certification works in the US.