Lowering the price could help, but the lower price options on the market have so many hidden costs Apple could probably keep the price the same if they just marketed the AppleTV like they cared that it existed?
The lower priced options on the market are subsidized by the data their manufactures collect about their customers then sell...
Add to that the number of big box stores that sell "installation service" for ~$50/box that amounts to nothing more than plugging it into power and HDMI and walking away... sometimes they may connect it to wifi.. maybe... (the total price of a slow as molasses in January "affordable" Roku after that bull-butter is HIGHER than a refurb AppleTV... can't make this ish up...)
Apple could probably expand their market more by promoting the privacy angle (They know everything you're watching you dirty dirty boy!) and how easy it is to get setup and streaming.
But, let's be real.
Apple will probably never do either of those things.
I really would love to see Apple market tvOS & Apple TV – distinctly from tv+ – using TV advertisements, billboards & bus shelters in a punchy way like they used to with iPod.
In print, tell everyone it exists, mention the privacy, and describe how it unifies TV streaming services into one queue. On TV, show everyone how it's better than the competition.
(Also, throw in a year's tv+ subscription when you buy, give people a lengthy chance to experience the content.)