Yes, I see many places over-charge for genuine Mikuni jets. Retail on the mains and pilots is only about $4 each but I see many places charging $6 or more. Luckily, they are very common jets and available from many places. The main jet style is what's called a large round main. It's Mikuni # is N100/604 .....
The pilots are the BS30/96 type. They are similar to the VM22/210 style used in some of the earlier carbs and will interchange, but you must use the BS30/96. The carbs are designed for it. A VM22/210 will physically fit in there but it won't flow correctly.
I buy my jets in 4 packs from the "big box" places. That's the cheapest way I've found .....
https://www.chapmoto.com/mikuni-kn100-604-large-round-main-jet-parent-342-1561
I see from the link you provided to that dyno kit that the needles are from the 7 series. That would make them quite a bit longer and leaner than the stock 5 series needles. Mikuni needle series come in 10mm length spans. A 5 series spans 50 to 60mm in length, a 6 series 60 to 70mm, etc. Being that needle adjustment slots are 1mm apart and changing just one step can make a big difference, you can just imagine what a 20mm difference in length could do. Frankly, I'm surprised that needle even works at all. But, most reports are it doesn't work, at least not very well.
Apparently that kit was designed for use with a 750 big bore kit and Heiden's own (designed by them) 2-1 exhaust. You don't have either. Also, many times jetting specs used in Europe with their fuel mixes don't work right here with our gas.
I think the first thing I'd do is ditch that needle and maybe try the stocker again, or one of the adjustable ones available that are closer in length to it.
