One more option for some people who have strong technical skills, so I realize it might not work for you, but I just mention it for others who might be reading along…
Also, this is pretty much the opposite of the approach that works for me as it takes time and tinkering, as well as meticulously following multi step technical instructions. But if you’re up for all that and you have a SmartThings/Aeotec hub, the following is a possible option to saving a lot of money building out your smart home. 
There are literally hundreds of very inexpensive WiFi devices that can be “flashed’ with Tasmota firmware. This will violate the warranty and leave them unusable with their own app—but it will let you use them with a community-built edge driver to bring them into SmartThings.
Again, you have to read all the instructions and follow them precisely—one false step could leave the device unusable and unrecoverable. 
But if you enjoy hacker projects and you have strong technical skills, this is a popular budget option.
Sonoff WiFi devices and Tuya WiFi devices (not the Zigbee models) are probably the best known brands that you can do this with, but there are lots more. Safety certifications vary a lot, so select carefully if that’s important to you. Also if you are in North America, read product descriptions carefully: many of these devices are intended for Asian markets and have different current and load specs. (Oh, and going this route may strip the device down to its basic on/off/dim features, particularly for Tuya. So you may need to do extensive research before starting to find out what features a particular model will end up with.)
Here’s the thread about the edge driver (the topic title is a clickable link).
Again, speaking personally, I’d rather spend $9 for a Meross ETL certified smart plug that just works out of the box, supports 15A, and I can buy from Amazon than spend $4 for a no name no safety certification device limited to 10A that I had to scour AliBaba for and then spend several hours getting it to work with custom code, but that’s just me. Choice is good. 