I paid extra for more leg room on my last Delta flight. I believe it was around $60.
Here's a list of extra fees from Delta.
In-cabin pet fee: $125- I didn't know you could take your snakes on a plane.
http://www.airfarewatchdog.com/blog/3801089/airline-baggage-fees-chart/
Baggage fees are one of the most irksome aspects of the air travel experience to some travelers.
But travel technology company Sabre Corp. said this week that a survey it conducted showed that 80 percent of travelers bought extras on their last trip and spent an average of $62 on those extras. Those survey respondents also said they would spend more to improve their travel experience up to $99, according to Sabre. Sabre makes software for airlines to manage flight reservations, revenue and other activities, processing billions of dollars of travel spending annually.
http://airport.blog.ajc.com/2016/10/29/how-much-are-you-willing-to-pay-in-airline-fees-for-a-better-travel-experience/Sabres survey showed that the services travelers are willing to pay extra for varies depending on the region of the world.
North Americans and Europeans like preferred seating and extra leg room, for example.
Latin Americans prefer on-board wi-fi. Asia Pacific travelers are most interested in extra checked baggage.
Those in Africa are willing to pay extra for on-board food and beverage, and travelers in the Middle East like fast-track security.
Overall, the most desired extras were upgrades, on-board food and beverage, preferred seating and extra leg room. The next most popular extras were in-flight wi-fi and extra checked baggage.
Here's a list of extra fees from Delta.
Delta:
Ticketing Fees
Non-refundable ticket change fee: $200 (up to $450 on some international fares)
Same day change fee: $50
Reservation by phone or ticket office fee: $25-$35
Unaccompanied minor fee: $100
Baggage Fees
Carry on bag: Free
First checked bag fee: $25 ($0 to international destinations except Canada and Caribbean)
Second checked bag fee: $35 ($40-$100 for some international destinations)
Additional bags fee: $125 for third bag; $200 each for bags 4-10
Overweight bags: $90 for 51-70lbs; $175 for 71-100lbs
Oversize bags: $175-$300 (These fees may be higher or lower for some international destinations and are waived for some elite level frequent flyers, active military, American Express SkyMiles Cardmembers, etc).
In-cabin pet fee: $125
Frequent Flier Fees
"Last minute" ticketing: $0
In phone/in person ticketing: $25
Date/itinerary change: $150 (warning! no changes/cancelations are permitted within 72 hours of departure; all miles forfeited)
Redeposit Miles: $150 (no changes/cancelations are permitted within 72 hours of departure)
Same day change fee: $50
Other Fees
Seat Selection Fee: $9-$59 for "preferred seats" per segment.
Priority Boarding Fee: $10 per flight.
Name Change Fee: Not offered.
Other Fees: $9-$180 per segment for "Economy Comfort" seating.
In-cabin pet fee: $125- I didn't know you could take your snakes on a plane.
http://www.airfarewatchdog.com/blog/3801089/airline-baggage-fees-chart/