Specifically, I am in the market for an engine ($25,000+), constant speed propeller ($7000) and at least $10,000 worth of avionics. What did I find? SFA.
You found your engine and you found Garmin and I'm sure Dynon was probably floating around there somewhere however you probably couldn't have made a purchase anyway. It's not a retail shop at Avalon, it's a trade display / hall. Quite different. They just point you to the nearest vendor to you that stocks their wares and you go there and make your purchase. Buying from Avalon generally speaking would be like buying direct from the manufacturer and they aren't all set up for that.
Seems that at OshKosh as well as the vendors, there are lots of small pop-up shops like Sporties and Aircraft Spruce where you can buy your kit and walk home with it. That's what we are missing here to keep Sunny happy and I can understand the gap and why it's frustrating. Probably the reason why Jack Ranga was so happy when he got to OshKosh and gave his card a workout. I remember buying heaps of kit at Aircraft Spruce when I was at OshKosh as there was no freight costs.