fee:conditional looks fine to me. Maybe it complains about the missing space between yes and @?
Do you have to specifically buy the day/week pass? Then it’d be clearer to tag it like 3.00 EUR/day @ daypass; 7.50 EUR/week @ weekpass
If it’s automatic, you can leave it like you did. Not sure what JOSM complains about.
The weekpass has to be bought seperately via a dedicated button. The daypass is probably calculated automatically from the estimated stay duration the customer has put in (it’s paid upfront). I only took a picture of the machine - I didn’t try it out. i’m also unsure if it’s even possible to purchase two daypasses at once - that is just an assumption.
I found OSM Conditional Restrictions as an online tool to create conditional restrictions and it works just fine, so I’d just ignore JOSM at this point.
As to the passes, I’d just add it with the daypass/weekpass conditions and leave it to others to check if a valid daypass has been purchased.