It takes 90 searches to get a guaranteed S rank. Each master tape costs 160 polychrome, so you'd need 14,400 polychrome to get 90 quickdraws. Getting that many polychromes through the monochrome market costs about $220, which seems like a lot for a single character.
Am I missing something about how to get master tapes?

Accumulating 14,400 polychromes through the monochrome market is really expensive and time-consuming to get 90 master ribbons and a guaranteed S rank. There are other ways, such as participating in events, daily tasks or in-game exchanges, which can help accumulate the required amount of resources without spending a lot.
For a quick balance replenishment, you should pay attention to Top up ZZZ online - this is a convenient way to replenish polychromes and other game resources directly through trusted platforms, which can save time and simplify the process.
You just need to carefully monitor in-game promotions and use different sources of replenishment to manage resources as efficiently as possible.

Thanks for the answer. I was just thinking about trying to collect some polychromes through tasks and events, but I wasn't sure how much it would really give. Now I'll be more attentive to promotions and will definitely use the convenient ZZZ top up, so as not to overpay and at the same time not to miss the chance for a guarantee.