I'm lazy to click around on klm's website.
Sample output:
~/go/src/github.com/dominis/martykaan master ● go run main.go
#### Bestest ####
origin: BUD-2018-06-07 | destination: AMS-2018-08-14 | lowestfare: 189.42EUR
origin: AMS-2018-06-07 | destination: BUD-2018-07-11 | lowestfare: 242.19EUR
*** AVG per flight: 215.81 EUR ***
#### Bestest ####
origin: BUD-2018-06-14 | destination: AMS-2018-08-18 | lowestfare: 311.22EUR
origin: AMS-2018-06-14 | destination: BUD-2018-07-21 | lowestfare: 167.19EUR
*** AVG per flight: 239.20 EUR ***
#### Bestest ####
origin: BUD-2018-06-21 | destination: AMS-2018-08-14 | lowestfare: 218.27EUR
origin: AMS-2018-06-21 | destination: BUD-2018-07-21 | lowestfare: 191.19EUR
*** AVG per flight: 204.73 EUR ***
#### Bestest ####
origin: BUD-2018-06-28 | destination: AMS-2018-08-14 | lowestfare: 166.03EUR
origin: AMS-2018-06-28 | destination: BUD-2018-07-21 | lowestfare: 184.19EUR
*** AVG per flight: 175.11 EUR ***
#### Bestest ####
origin: BUD-2018-07-05 | destination: AMS-2018-08-14 | lowestfare: 124.36EUR
origin: AMS-2018-07-05 | destination: BUD-2018-07-21 | lowestfare: 207.19EUR
*** AVG per flight: 165.77 EUR ***
#### Bestest ####
origin: BUD-2018-07-12 | destination: AMS-2018-08-14 | lowestfare: 166.03EUR
origin: AMS-2018-07-12 | destination: BUD-2018-07-18 | lowestfare: 229.19EUR
*** AVG per flight: 197.61 EUR ***
#### Bestest ####
origin: BUD-2018-07-19 | destination: AMS-2018-08-14 | lowestfare: 115.06EUR
origin: AMS-2018-07-19 | destination: BUD-2018-07-21 | lowestfare: 233.19EUR
*** AVG per flight: 174.13 EUR ***
#### Bestest ####
origin: BUD-2018-07-26 | destination: AMS-2018-08-14 | lowestfare: 115.06EUR
origin: AMS-2018-07-26 | destination: BUD-2018-11-21 | lowestfare: 207.19EUR
*** AVG per flight: 161.13 EUR ***
#### Bestest ####
origin: BUD-2018-08-02 | destination: AMS-2018-08-14 | lowestfare: 157.05EUR
origin: AMS-2018-08-02 | destination: BUD-2018-11-21 | lowestfare: 220.19EUR
*** AVG per flight: 188.62 EUR ***
#### Bestest ####
origin: BUD-2018-08-09 | destination: AMS-2018-08-14 | lowestfare: 157.05EUR
origin: AMS-2018-08-09 | destination: BUD-2018-11-21 | lowestfare: 184.19EUR
*** AVG per flight: 170.62 EUR ***
#### Bestest ####
origin: BUD-2018-08-16 | destination: AMS-2018-08-18 | lowestfare: 401.92EUR
origin: AMS-2018-08-16 | destination: BUD-2018-11-21 | lowestfare: 124.19EUR
*** AVG per flight: 263.06 EUR ***
#### Bestest ####
origin: BUD-2018-08-23 | destination: AMS-2018-08-28 | lowestfare: 174.36EUR
origin: AMS-2018-08-23 | destination: BUD-2018-11-21 | lowestfare: 135.19EUR
*** AVG per flight: 154.77 EUR ***
#### Bestest ####
origin: BUD-2018-08-30 | destination: AMS-2018-09-01 | lowestfare: 194.23EUR
origin: AMS-2018-08-30 | destination: BUD-2018-11-21 | lowestfare: 164.19EUR
*** AVG per flight: 179.21 EUR ***
#### Bestest ####
origin: BUD-2018-09-06 | destination: AMS-2018-09-08 | lowestfare: 146.15EUR
origin: AMS-2018-09-06 | destination: BUD-2018-11-21 | lowestfare: 184.19EUR
*** AVG per flight: 165.17 EUR ***
#### Bestest ####
origin: BUD-2018-09-13 | destination: AMS-2018-09-15 | lowestfare: 174.36EUR
origin: AMS-2018-09-13 | destination: BUD-2018-11-21 | lowestfare: 184.19EUR
*** AVG per flight: 179.27 EUR ***
#### Bestest ####
origin: BUD-2018-09-20 | destination: AMS-2018-09-22 | lowestfare: 157.05EUR
origin: AMS-2018-09-20 | destination: BUD-2018-11-21 | lowestfare: 184.19EUR
*** AVG per flight: 170.62 EUR ***
#### Bestest ####
origin: BUD-2018-09-27 | destination: AMS-2018-09-29 | lowestfare: 146.15EUR
origin: AMS-2018-09-27 | destination: BUD-2018-11-21 | lowestfare: 184.19EUR
*** AVG per flight: 165.17 EUR ***
#### Bestest ####
origin: BUD-2018-10-04 | destination: AMS-2018-10-20 | lowestfare: 147.84EUR
origin: AMS-2018-10-04 | destination: BUD-2018-11-22 | lowestfare: 138.49EUR
*** AVG per flight: 143.16 EUR ***
#### Bestest ####
origin: BUD-2018-10-11 | destination: AMS-2018-11-10 | lowestfare: 130.53EUR
origin: AMS-2018-10-11 | destination: BUD-2018-11-27 | lowestfare: 138.49EUR
*** AVG per flight: 134.51 EUR ***
#### Bestest ####
origin: BUD-2018-10-18 | destination: AMS-2018-10-27 | lowestfare: 190.79EUR
origin: AMS-2018-10-18 | destination: BUD-2018-11-21 | lowestfare: 122.49EUR
*** AVG per flight: 156.64 EUR ***
#### Bestest ####
origin: BUD-2018-10-25 | destination: AMS-2018-10-27 | lowestfare: 190.79EUR
origin: AMS-2018-10-25 | destination: BUD-2018-11-21 | lowestfare: 138.49EUR
*** AVG per flight: 164.64 EUR ***
#### Bestest ####
origin: BUD-2018-11-01 | destination: AMS-2018-11-10 | lowestfare: 97.84EUR
origin: AMS-2018-11-01 | destination: BUD-2018-11-21 | lowestfare: 98.49EUR
*** AVG per flight: 98.16 EUR ***
#### Bestest ####
origin: BUD-2018-11-08 | destination: AMS-2018-11-12 | lowestfare: 79.89EUR
origin: AMS-2018-11-08 | destination: BUD-2018-11-21 | lowestfare: 121.49EUR
*** AVG per flight: 100.69 EUR ***
#### Bestest ####
origin: BUD-2018-11-15 | destination: AMS-2018-11-17 | lowestfare: 97.84EUR
origin: AMS-2018-11-15 | destination: BUD-2018-11-21 | lowestfare: 121.49EUR
*** AVG per flight: 109.66 EUR ***
#### Bestest ####
origin: BUD-2018-11-22 | destination: AMS-2018-11-24 | lowestfare: 72.20EUR
origin: AMS-2018-11-22 | destination: BUD-2018-11-27 | lowestfare: 89.49EUR
*** AVG per flight: 80.84 EUR ***
####
Summ avg: 166.33 EUR