These are hard to find on discount. $24 on Bing Lee eBay store. Use code SAVE5TB for 5% off, eBay Plus members use SAVE7TB for 7% off, Max $100 off. Can buy in store, click and collect, or delivery. $27 at JB HiFi (will price match). Not sold on Amazon but Amazon does have the non power monitoring smart switch for $18 (normally $24.95).
TP-Link have the Tapo and Kasa smart home ecosystem. Different apps. The big difference is that the Tapo app lets me share devices I choose with other accounts so that they can control the switch. Kasa doesn't let me share a device and instead I have to give the other person my account details. The Tapo app also lets me see the day to day power usage whereas the Kasa app is less informative. iPhone users can download the free third party Watt app which combines control of the Tapo and Kasa power monitoring smart switches. The biggest real world difference between Tapo and Kasa in my experience is that Tapo lets me share control of the devices with others. Tapo also works with Alexa, Google Assistant, and Siri whereas Kasa does not.
I had the exact opposite between the 2 brands. Kasa would show me energy usage and Tapo would not - I ended up refunding all my Tapo gear because I couldn't get energy usage and I couldn't integrate it into Home Assistant.
I did not try the sharing Kasa between devices though as we use Home Assistant to control them.