TLDR: US operas tickets $35-350, symphony tickets $35-200. There are reasonable prices if you're interested.
Classical music is expensive, and ticket sales rarely even cover half of an orchestra's operating budget. The rest comes from wealthy donors. An arts organization asking for donations is standard practice.
Tickets are sold in a wide range of prices depending on the seat. I've done a little digging on ticket price ranges of major US cities that have both operas and orchestras.
Seattle Symphony $35-135
LA Phil $20-190
Dallas Symphony $46-253
Chicago Symphony $49-250
NY Phil $72-180
Seattle Opera $67-399
LA Opera $34-346
Dallas Opera $19-482
Lyric Opera of Chicago $41-297
Metropolitan Opera $47-465
In addition, most orchestras have much cheaper rush tickets or discount codes. If you are interested in classical music but can't afford the tickets look into these options.
When the previous commenter said tickets are $300 I got suspicious. Though opera companies do sell $300 tickets those are near the top of the price range.