I believe the Wilbur D. May Museum is completely separate from the Dragon Lights. You can see the Sierra Watercolor Exhibit and some other exhibits at no charge, but for parts of the Museum there is a fee (lower than $20).
Looks like general administration is 20.00 and you can buy them from dragonlightsreno.org. there are also walk-in tickets but they have a surcharge
Thanks! Your answer is awaiting moderation.