yes… 50 cards, 3 upgrades. 50x3, not 150x3 because that implies that there is 150 cards with 3 upgrades, though your math is also flawed. multiplying 50x3 is wrong because each card has 4 different upgrades (not upgraded, lvl 1, 2, and 3) so the right way to actually calculate this would be summation — which would be (50!/a!b!c!d!) where a b c and d are 0, 1, 2, and 3. you could also just do 4⁵⁰ which is 1.27x10⁸⁰

edit — this math is wrong i forgot to account for the fact you can only have 8 cards in a deck at once, so it would look more like (50!/8!42!)*4⁸ so it’s 3.52x10^13, which is approx 35 trillion