There is a basic formula you can use for cash bonus post wager promotions such as videoslots.
ev = bonus - wagering x house edge,
For these types of promotions, they aren't very good but are better than playing with just your own cash. the viability of the playthrough requirements is directly linked to the RTP of the game you play as 96% slots would be break even at 25x wagering.
People often erroneously apply this formula to normal deposit matches which leads to a lot of misunderstandings about the actual value of deposit bonuses. Due to not actually finishing wagering every time (25% being the average probably on a pretty normal offer), the formula falls apart.
I've explained in detail in other posts but I won't bore anyone with that again. With that said, in short, for an accurate EV figure you need to do simulations. Volatility plays an important role whereas before it wasn't relevant.
As with post-wager, the playthrough requirement alone doesn't determine viability and is dependent on the other factors. You can have an offer with x100b wagering and still be viable if the max stake and RTP are high enough. I think x70b is usually the highest I would do with relatively normal terms. A good thing to remember is that if the rules of the bonus are high wagering, low max stake and capped winnings, that is not a bonus you want to play.
