What if the cost was 300/275/250/225/200$ at start (based on how many points in ultimate), but the cost of the ultimate REDUCES by 1$ for every second elapsed in the round?
This would make the race less about being instantly bulky at round 1 or start, but becomes more of a lategame sustain race the more time you're on it in the round? Especially seeing as the Bloodmage is usualy limited to 2 per team?