It probably depends on the book, but I have often found Kobo books to be less expensive than the Kindle books I've been considering purchasing, which actually surprised me.
I check this thread here, too:
https://www.mobileread.com/forums/sho...d.php?t=115233
Not every book is eligible for a discount, but it doesn't hurt to check.
I have a Vox and an iPad with Kobo and Kindle apps, so I price check and go with the best deal before I make a purchase. My first reader was a Sony PRS 650, which doesn't see a lot of use anymore because it doesn't have wifi (but it has a much better battery life when I do use it). I've purchased at the Sony store, but price-wise it has never been any less expensive.
I do get a lot of freebies from Amazon. Kobo's selection of free books doesn't even come close in comparison.
I also borrow a lot of e-books from our public library system. I use the Overdrive app on the Vox and iPad, and the Sony device's software is already compatible. Where I live, you can't do that with a Kindle.