Melissa Clark's Instant Pot books have been on sale on Amazon.
Right now, Dinner in an Instant is $3.99 on Amazon US and it even looks like it might be on sale on Amazon Canada as well. (Not sure if this link will properly take you to Amazon Canada or not, it seems to revert to US when I use it down here. If that makes any sense.)
Comfort in an Instant was on sale yesterday for $3.99 but when I went to post about it, it had gone back up in price. If interested, it may be worthwhile to keep checking the price.