Cheap is rarely ever better. How did you like the cutters on the Easy Wood tools when they were new? If you did spend the $20 and get the same cutter. They go 20 - 40 hours per “side”. For me I use the original cutters. Much better. Just saying …
You specifically stated the negative rake cutters... I have found some other flat cutters, but I don't know that I've ever come across negative rake cutters that work in an EWT tool.
They should last a while. For the round cutters, when I first put a new one in, I take a black sharpie and mark the left "corner" where the depression at the end of the bar starts and the carbide tip sits, and draw a line on the cutter right there. I then rotate little by little from there, until that black line is about 1 rotation away from where it started. I guess I rotate only a few degrees each time, as I tend to use the tools (with pens anyway) in such a manner that only one part of the tip is ever in contact with the blank. So they should last a while. At $20 a tip, its not a bad deal IMO.
I use the Easy Wood Tools, Mid-Size chisels but in addition to their branded cutters, I have used cutters from Ron Campbell at AZ Carbide.
AZ Carbide is located in Michigan and is owned by Ron who is an award winning wood turner. In my personal experience, the AZ Carbide cutters provide comparable results with those from EZ Wood Tools at a significantly lower cost. For example, the square cutters with 2-inch radius edges were only $6.80 each the last time I bought them in a 10-pack compared with the Easy Wood Tools Ci1-R2 cutters at $18.99 from our local WoodCraft store. The AZ Carbide website has a cross reference chart between various brands of tools and AZ Carbide cutters.
Regarding the subject of negative rake cutters and comments already posted from others, the Easy Wood Tools NR (Negative Rake) carbide cutters are patented and trademarked by Easy Wood Tools, so it is unlikely that you will find carbide cutters with the negative rake angle ground into them from anyone other than Easy Wood Tools.
That being said, there are still alternatives. Standard carbide cutters have a neutral or zero rake. Rake is the angle of the tool or cutter relative to its cutting surface. A negative rake is when the face of the cutter slopes away from the cutting edge. The geometry and cutting forces with a negative rake angle makes less aggressive cuts which helps eliminate chatter and chipping of brittle materials. About a year and a half ago I made some tools where the mounting surface for the cutters was ground so that the cutter presented with a negative rake when the tool itself was still held level. So far, for me anyway, they have been working just as well as the Easy Wood Tools NR cutters. I attached a few pictures of one of the tools that I made along with the notes I made when I was doing the related research. (The notes show a standard "flat" cutter and how it presents to the work along with how an Easy Wood Tools NR cutter presents and how my tool with a standard carbide cutter presents.
The easiest option for the negative rake cutter is to use a normal cutter and flip the tool upside down thereby creating a negative rake. You want to cut above center. Or put on 1 of your regular old dull blades. They work too and both options are free.
As for other cutters that you can't sharpen, I just buy a pack off ali express or Ebay. But you need to measure the size your blades are and the hole size.