Why would someone pay more for instant funding?
Pretty simple.
They don't want to spend weeks trying to pass an evaluation, or waiting profitable trading weeks on challenges.
For a trader who values speed over price, paying more upfront can make perfect sense.
The consistency rules are tighter, but ultimately the required balance needed to get a payout is less. In other words, you need to make less money to get paid.
Every trader goes through up and downs, there is nothing worse than making $4k including challenges, plus some profit, then letting it slip and getting paid nothing.
With an Instant funding, that would be profit in your bank.