We've sold a modest number of EX650s since their release, and have never seen one that even seemed to need a valve clearance check at 600 miles. While it's theoretically true you can't be too safe, it would really be a waste of money. Don't worry about it.
Unless your model really does require a valve inspection, according to the manufacturer, a first service for most bikes should not cost $300. $150 is about right, YMMV. Since modern bikes really don't get out of whack until they have a lot of miles on the clock, what you get for your money, besides the oil change, is for a truly experienced professional to do a 360 loop around your bike and check every major system or component.
A guy, or lady-type, who handles many different bikes every day will quickly spot things that need adjustment, but it doesn't need to be a dealership - the handful of folks on this site that work as private techs seem to have enough background and daily experience to do it more or less as well. A dealership should be sending all its techs to the manufacturers' update seminars, though, and that can give dealer staff a little advance notice if the factory techs have been frank enough to say, look for this problem on this model, we saw it a lot in development. But most bikes these days are so good, it's less of an issue.
As long as you keep your receipts that show oil & filter purchases, or aftermarket shop bills that show some kind of maintenance, in most cases you don't need to go to an OEM dealer for service to maintain the warranty. Again, YMMV. That is, if there's an electrical issue, or a weld failure or a crack on a fender, it won't matter who did the 600 mile oil change and inspection.
In the last 4 years, with over 1500 new bikes sold, we have seen only one person not be able to claim a warranty issue because he didn't have a dealer do his services. This was a young guy with a Hyosung GT250R that he bought from us, that came in at 4000+ miles with the engine making loud knocking noises. We found less than a quart of oil in the motor, and it was like tar. We checked our service records, and he hadn't been in since the purchase, and hadn't bought any oil or OEM filters from us either. His father insisted that he'd seen the guy do at least one oil change, but couldn't show any receipts from anybody, and it's not like there's a Hyosung dealer everywhere. As far as we could tell, he had simply run the motor since new without any service or added any oil, and the motor had used up enough of the original oil to burn up its top end. We told him that Hyosung probably wouldn't pay for an engine rebuild under the circumstances, but if he could show some receipts from anybody we'd go to bat for him. They've never come back.
On the other hand, we have seen all our OEMs greenlight various warranty repairs that were kinda questionable. Most of the time, they prefer to keep the customer happy.
