As discussed HERE it would appear that card costs are not necessarily always a set thing. According to the poster, if you boost a card before using it as a booster, it will cost more than just a plain ol' card used at that level. I'll be randomly trying to track these numbers here. So, for the moment this is just a place holder blog until I figure out what kind of chart I'll be using...because I love tables. XD
At the moment, I've just used my Lv. 24 [Lie-Smith] Loki as a base card, and then verified with a few random cards that the boost cost is 2205.
Using a common Thing that is presently at level 7, cost 2475.
Using a level 2 Iron Fist, it was 2250.
Using a UR+ Spider-Man at Level 70 costs 5310.
Using Level 10 - 2610
Using Level 21 - 3105
Using Level 3 - 2295
So...based on all this alone, it's 45 extra silver per level of a booster after level 1. No table necessary!!! :D (EDIT) I spoke too soon...dang it...stay tuned for more... XD
A 21 base costs 1935 for level 1 boosters. Level 2 booster costs 1980. 3 = 2025. 60 = 4590 which is 2655 (45*59) + 1935. So...in both of these cases, 45 silver is the magic number.
A 1 base costs 75. 2 = 100. 3 = 125. 60 = 1550 which is 1475 (25*59) + 75. So, for a level 1 card, it's 25 silver.
A 10 base costs 735 for level 1 boosters. 2 = 770. 3 = 805. 60 = 2800 which is 2065 (35*59) + 735. So, 35 silver.
At this point the pattern seems to start at 25 silver for levels 1-9 of a base. 35 for 10-19 of a base. 45 for 20-29 of a base. So, at this point my assumption is that for every new bracket that a base card will fall under for its level, the modifier will also increase by ten silver starting at 25 for 1-9. I'll try and organize this a little better. Don't know when or if I'll bother verifying each and every level that this is true.