What decides the price
Two things: the account size and the programme. Bigger accounts cost more because the potential rewards are bigger. Programmes with smaller targets or tighter limits (Ascent, Spark) are cheaper; programmes that fund you faster (1-Step) cost a little more; Pass lets you pay a small fee first and the rest only if you pass.
How to compare prices between firms
Divide the fee by the account size to get the cost per $1K of capital, then check whether it is a one-time fee or a monthly subscription. Look at what you get for it: the targets, the loss limits, the profit split and how payouts are sent. A cheap challenge with tight rules can cost more in retries than a fairer one.