Agencies: retainer + % of spend
The most common agency model is a monthly retainer plus a commission on ad spend. At ₹5,00,000/month in spend, even a modest commission becomes a large number — on top of the retainer. The daily work did not get harder; your bill did.
Freelancers: recurring, variable
An Amazon PPC freelancer can be cheaper than an agency but quality and availability vary, and the cost still recurs monthly. Good for projects; less predictable for ongoing daily management.
Software: one flat fee
Automation like AIAdKing is a flat ₹2,499/month ($7.49) with 0% commission — the cost is the same whether you spend ₹50,000 or ₹50,00,000. As spend grows, flat-fee software gets dramatically cheaper than any percentage model. See pricing.
Work out your real number
Add the retainer to the commission on your actual spend and compare it to a flat fee. For most sellers past a modest ad budget, the percentage models cost multiples of software for the same daily work. The best PPC tools comparison lays out the options.