Concerns About Clay Pro Plan Credit Costs and Upgrades

Hey Clay team, I am regularly needing to top up my clay account and i have reached the top tier “Pro” plan of 150k credits. Why dose it cost 1.5 x more to purchase additonal bolt on credits? This seems a little unfair. Is there a higher plan i can go on above 150k credits? I dont want to pay for 12 months upfront so is there anything we can do?