They vary enormously (just like the forex prop firms do).
They have special offers and discounts and stuff, on and off.
At the moment I believe Topstep is $50 for a $50k account with no time-limit, but theirs is a monthly charge, not a one-off, so it might really cost you $100 or even $150 if you’re not in a hurry at all.
Tradeday is one of the best, currently 40% off, but also monthly (slightly lower profit target than Topstep and no daily loss limit - they vary!).
Apex is the cheapest (it’s almost always either 80% or 90% off, but that’s probably the only way they can get customers at all, and there are a lot of reports of “payout problems” there at the moment, and the company is owned and run by a former scammer from a crooked “binary options” business - I definitely wouldn’t touch it, myself!! It’s the only crooked one, though, as far as I know).
My guess is that overall, they’re probably very slightly more expensive than the forex ones.
But you end up being genuinely funded by and doing business with a genuine partner who can win only when you win, and wants you to do well, on a genuine, transparent exchange with no trickery, etc. etc. It’s really a whole different world.