After doing a big of research on line and in discussion with a friend, I bought my first aids from Costco almost a year ago now - KS8’s. No regrets at all in going to Costco. I have been difficult to fit due to a substantial loss in my left ear. Have lost track of the number of times I have been back for adjustments. Most of them were at my initiative, in wanting to try something different for prescription formula or fittings. I eventually got impressions for custom molds and tried them for 3 months, but could not tolerate them in my ears. They gave a me a full refund with no questions asked. They do not charge for audiograms, follow up fittings, replacement off the shelf fittings, and wax guards. Their standard is to do a full REM test and adjustment when any change is made to the targets or fittings.
The current KS9 aids are very similar to the Phonak M90 Marvel aids but with a 312 battery, no tinnitus option, a more basic app, and no Roger compatibility. Basic functionality is the same as the M90. They are a very good buy if they are suitable for your needs at $1500 a pair. They do have other options with name brands on them, but will cost more.