I recall in the UK in 2006, in retail supermarkets, it's been disclosed that the tag price is a cash-only price. That if you pay by a credit card, then the price is 2 or 3% less, but there's an extra 2% or 3% fee for credit card processing.
In the US, sales tax is almost never included in the price tag, so, when you checkout, you get the sales tax itemised separately, including when different jurisdictions charge separate taxes (e.g., county + city sales tax). Hotels in states with a gross-receipts tax often pass this tax back to the consumer as well.
In Eventbrite and many other similar apps, including for donations, the processing fees are nearly always shown separately from the cash price itself; I believe some platforms let the seller decide how it's shown (e.g., "who pays it").
Tax break downs are also posted at the pump when buying gas in the US, because they are so high. Which is kind of the point in the case of the app store as well. They would have more sympathy from me if they charged a more reasonable fee.
In the US, credit card companies don't allow sellers to disclose credit card fees or charge separately for them. You do sometimes see a discount for cash, which is probably due to lax contract enforcement, and, of course, many sellers only accept the subset of credit cards with the lowest fees.
Are you sure the sellers aren't allowed to disclose the fees? I believe the sellers aren't allowed to charge more on CC than the cash price. Note that the example above may be a little convoluted if you aren't too observant a reader, but the whole idea is that the total price that the user pays is still the same regardless of the method of payment, it's just that the money are allocated differently, with the user being informed of the allocation.
In the US, sales tax is almost never included in the price tag, so, when you checkout, you get the sales tax itemised separately, including when different jurisdictions charge separate taxes (e.g., county + city sales tax). Hotels in states with a gross-receipts tax often pass this tax back to the consumer as well.
In Eventbrite and many other similar apps, including for donations, the processing fees are nearly always shown separately from the cash price itself; I believe some platforms let the seller decide how it's shown (e.g., "who pays it").