Did some math that I found interesting.
The chance of rolling a banner character/skillset is 1% per roll. Calculating how many times you might roll the character in a given number of rolls is complicated, but calculating the chance that you will roll the character at least once in a given number of rolls is easy. This is because the odds that you won't roll the character at ALL is just the probability of losing per roll (99%) multiplied by itself a number of times equal to how many times you roll. So the odds that you won't get the banner character at all in 10 rolls is 0.99^10 (90.4%) and the odds that you won't get the banner character at all in 100 rolls is 0.99^100 (36.6%)

For one thing, this illustrates that spending tickets when you're not prepared to go all the way to pity is a bad idea. You could drop 1000 tickets and your odds of getting the banner character would only be slightly better than a coin flip (63.4%) and if you fail, there goes nearly a whole season's worth of tickets.
But I noticed something else interesting. The number of tickets you spend relative to the probability you get seems to increase as you spend more tickets in total.
For example, if you spend 100 tickets, you have a 9.6% chance to get the banner character. This means each 1% probability "costs" 10.5 tickets. If you spend 1900 tickets, you have an 85.2% chance to get the banner character, but each 1% probability costs 22.3 tickets.
Unless I've got an error in my math somewhere, it seems like the value of tickets relative to the increase they provide in your odds actually gets worse as you spend more and more. I mean, spending more tickets DOES increase your (cumulative) chance, but it gets relatively more "expensive."
The increase seems to be fairly linear, pic related.