Start with $.50/click. Adjust down if you're having trouble filling inventory; adjust up if you're consistently booked.
From there, the math is simple:
sticker_price / (subscriber_count * click_rate). The median came out to a very satisfying
This is, of course, a naive inquiry — these numbers vary based on niche, brand reputation, and a thousand other things. But if you're jumping into sponsorships for the first time (on either side of the table!), this is a good heuristic to anchor to.
Some larger, more sophisticated sponsorships go instead with an affiliate model: rather than charging per click, they charge per conversion. Some examples as pulled from PostApex:
Affiliate pricing can be very attractive for two reasons:
...but it's hard to jump right into the affiliate game. Conversions are rare and noisy (meaning subject to statistical noise) relative to just having a simple sticker rate.