I used ITA to price out the flights you found on DL.com. Here is the tax breakdown - but as you can see the total is less than what DL.com gives.
Looks like the fuel surcharge is "only" €400.00.
Fare (A1): DL YAOCVG LLPXAFW5 fare (rules) , psgr type ADT XAF 367500
Fare (B1): DL CVGFYV KE21A0NA fare (rules) , psgr type ADT $132.10
Tax: US Transportation Tax $9.90
Fare (B2): DL FYVCVG KE21A0NA fare (rules) , psgr type ADT $132.09
Fare (A2): DL CVGYAO LLPXAFW5 fare (rules) , psgr type ADT XAF 367500
Tax: USDA APHIS Fee $5.00
Tax: US Immigration Fee $7.00
Tax: US Customs Fee $5.50
Tax: US International Arrival Tax $16.30
Tax: Cameroon Safety Tax XAF 10000
Tax: Cameroon Development Tax XAF 15000
Tax: Cameroon Passenger Service Charge XAF 10500
Tax: US Flight Segment Tax $3.70
Tax: French Aviation Civile Tax €14.98
Tax: French International Passenger Service Charge €28.04
Tax: French Airport Tax €25.50
Tax: DL YQ surcharge €400.00
Tax: US International Departure Tax $16.30
Tax: US September 11th Security Fee $7.50
Tax: US Passenger Facility Charge $10.50
Total for 1 adult passenger: $2571.00