make nitro conversions more accurate

so I’ve known for a while that the maths on the nitro prices I would have to pay are a bit off, but I just used a converter and for GBP the conversion is really off. I get that it might go up or down a bit for profit or to account for conversion prices, but it would cost me £2 more than it should for monthly full nitro.

Edit: after a small discussion with some other people, I get that conversion charges and App Store charges are included in this, but for example the 50p extra from monthly classic to monthly full shouldn’t be in there in my opinion (fixed rates are fixed rates, not curved ones)