There is no duty free at Liberia, this combined with the limit of liquids makes it essentially impossible to take alcohol back to Canada unless you have a checked bag.
In 2018 The BRITT store in the Liberia airport offers 6 free BRITT products with the purchase of 15 BRITT products (and some lesser deals at lesser quantities.) But it turns out … you can get a better deal on BRITT products by stopping in the Liberia Walmart before coming to the airport. In 2019 the San Jose airport offered “1 free when you buy 12”, same deal – buy before you get there.
So, as with most airports around the world, do your shopping before you get to the airport.
Both airports are set up for accessibility based on Costa Rica standards. If you are in a wheelchair, you may want to take the elevators when available rather than the extremely long ramps with no rest or turn platforms.