How do shoutouts usually perform for you folks?

What should I expect for followers in return on a page that has about 1.8 million followers and gets 20k-30k likes per image?

I want to compare a few, but want to hear how others members do too.

It will vary depending on how your account appears at first glance and if the shoutout is from an account that relates to your niche (if you even have one). If its niche elated maybe 1-3k gain if it's random and your account is random (and you aren't a hot girl with bikini pics) you will be lucky to gain 500.

I don't have experience from big accounts, but when i got a shoutout from a 30k account 1.5k likes per photo, after about 30 minutes i got around 150 follows.

That being said his account was NFL and so was mine