Are you for real? 4 champions per year is terrible, you could buy more champions in the old IP system + runes. In fact I started playing in season 4 and I bought atleast 4 6300 champions (Yasuo, Jinx, Lucian, Kha'Zix) + at least 12 other champions since you needed 16 to start playing ranked (some of which were 3150 and 4800) + a full AD and AP rune page.
Most champions are not 6300. Average BE cost of a champion is 3000, so this represents ~6 you get to choose (if you don't disenchant permanents) and 24 you do not, which is 30 per year.