Is the price of a SIM card generally standard across Israel, or are prices variable, such as much higher at the airport?
Just back from Israel and can now report that a sim card at the airport cost $20 more than on the vendor website: https://019mobile.com/ (i.e., $50 vs $29). A friend said she paid $20 for a similar card from another vendor, but I do not know the details of the plan.
Prices exhibit a lot of variation.
First, at the airport you get ripped off, for sure. See also the answers on @Yehuda_NYC's other question.
However, even regardless of that - Israeli communications providers are notorious for a combination of discounted sales + price gouging when they can get away for it. So it's very possible you could see a factor of 4 or higher of difference even in the fees that resident Israelis pay, if they're not careful.
Also, in recent years and specifically in 2019 there are spates of renewed competition with new cellular operators (or virtual operators) entering the market, taking prices down. A (resident) with a SIM can now get a decent plan for a monthly rate of ~15 NIS (~4.2 USD) per month for the first year, and ~30 NIS (~8.4 NIS) afterwards. So even the $29 rate of 019 Mobile is very high. Of course, those rates are for people who already have a SIM. Still, for 30 NIS you can get a HOTTalk package by Hot Mobile: 500 min voice, 500 SMS messages, 5 or 10 GB data, not exactly clear; expires in 10 days. This of course requires that you actually visit a HOT Mobile store/booth/service center.
Also, if you order a new SIM to be sent to you, you're often charged a lot - as much as 40 or 50 NIS.