Mortal Kombat X mobile is even more expensive.
You can buy 2000 souls for $99. Average cost of gold characters is about 390 souls. Each character can be fused to upgrade it 7 times (8 total purchases). There are almost 60 gold characters. So for $99 you can't even buy 1 character and upgrade him to max .
60 * 390 / 2000 * $100
$11,000 to buy every character and upgrade them to max level. That is if you could directly buy all characters which you can't.
Some characters can only be obtained through packs (lootboxes per say) and they are random when you get a rare carachter out of them. You don't get them very often at all. To get every character and upgrade the to max, I don't know how much it would take but if I were to guess I would bet it is probably over $80,000. This is not including silver characters some of which are also only obtainable in packs.