As I've been in the market for windsurfing equipment over the last 12 months and bought stuff locally and in other states, a question that repetitively came about: "How can I support my local Windsurf Shop by buying there?"
My experience is that it has been a lot more difficult to actually support the local shops for a variety of reasons:

Sales Taxes:
Stores outside my state won't charge state taxes, and while everyone is supposed to declare and pay taxes on purchases made out-of-state or on the internet, very few do because reporting essentially relies on the honor system and is rarely enforced! So, de-facto, this makes every out-of-state purchases cheaper (5% in Wisconsin).
I can imagine this being even more a factor for people in states like CA where sales taxes are much higher resulting in even better savings. So I can see this being the first hurdle that stores have to face in their efforts to make it attractive to the locals.

Shipping Costs:
An other issue is shipping cost: This is not systematic but I noticed that there is a likelihood for people buying in out-of-state stores to be offered the shipping. This is a good way for stores to attract customers who would normally won't consider a purchase that requires expensive shipping costs due to the distance. This also happens with in-state stores but not always. There has been a few times where the local store wouldn't offer the shipping fees and the store was far away enough that driving to pick up the gear wasn't practical.

Customer Loyalty:
Loyalty is earned through a few different things: quality of service, product availability, professionalism, friendship, good and fair pricing, etc. This is entirely dependent on the store, its "best practice" and standards of operation. But ultimately, selling at MSRP price rarely happens nowadays and resellers always have to cut a bit their margins to make customers feel good about getting a "deal". Stores that don't offer this to locals are missing on the opportunity to build loyalty with their most likely repeating customers.

So what is my point with all this?
Because I've been trying several times to actively support my in-state windsurf shops and I found it a lot more difficult than expected. I'm in favor of the idea that the market decides who thrives and who disappears, and some stores should ask themselves why is that they don't get the locals to shop more often at their place or what can they do to build loyalty with the locals. I think that having an active hub like a local windsurf shop around is a great thing for the local development of the sport, but not to the expense that everything local will cost 5% to 20% more than anywhere else.

So, looking at this through my little lenses, it appears that local stores could use a little creativity to earn my business, such as:
In-state purchases get an automatic discount on merchandise to offset out-of-state competition due to sales tax avoidance
In-state purchases get a customer loyalty program that makes their discount progressively more attractive overtime
In-state purchases get free shipping
At first sight, this would make me consider supporting my local store more actively because they are trying hard to win my business. It would also more likely make me reconsider my choice of product and brand if equivalent in performance.

So, I don't intend to creat a controversial conversation, but I just wonder if anyone has a different experience and perspective on the topic?

Unfortunately, there are no Illinois stores I know of anymore. The closest is Southport Rigging and Isthmus Sailboards. You kinda have to shop out of state.

Southport Rigging WAS my favorite store. Ralph didn't keep much in stock, but he never declined to order anything for me from the distributors at the lowest price possible. He repaired two of my boards also. Unfortunately he closed the windsurfing department of his store and retired this winter.

I live in Cedar Falls, Iowa. We don't have any dealers in Iowa. I could buy from The House in St. Paul MN, or Isthmus in Madison WI or Wind Power in Fond du Lac WI. Wind Power became my local shop because they support racing. I attend their Walleye Wagatta early in May and the Wind Power Championships the 3rd weekend in September. Wind Power also attends the Dam Jam at Polk City IA the third weekend in May and the Windsurfing Regatta & Unvarnished Music Festival in Worthington MN the 2nd weekend in June. So do I which gives me 4 opportunities to get gear without any shipping if I have my act together and pick it out ahead of time. Both their service and advice is excellent. I race in the Kona One Design class. Wind Power's Kona prices are as good or better than what I've seen elsewhere. Their events are well run, the staff is personable. I've had contact with Wind Power's owner, Kevin Gratton, 3 to 5 times or more a year since 2001. He is one of my friends.

I can second what's written here about Kevin or Ben (if he still works there) Really nice guys. Also, Fond du Lac is a great place to sail. Kevin let me camp in his backyard anytime I went up there.

Agree! Kevin and Ben at Wind Power are very friendly and have a tone of knowledge. Being almost the only guy windsurfing in Sheboygan, I'm trying to send them a few of my co-workers to learn windsurfing... no success so far! (Ben teaches wind and kite)
Their shop is awesome and in front of a great launch by SW, W, NW and N conditions. The stuff Kevin has kept over the years could serve to tell the history of the sport: Really cool to check it out!
I'd also love them to consider a customer loyalty program for the locals!