Supporter groups have called for "a fundamental overhaul" of Uefa's "disgraceful" treatment of fans after being allocated only a third of tickets for showpiece European finals.
Fans accused Uefa of "cashing in" and want "transparency" over Champions League and Europa League final tickets.
Some tickets are already available on third-party websites for £5,500.
Liverpool boss Jurgen Klopp also called for more "sensible and reasonable" decisions on where finals are staged.
Klopp said he had sympathy for supporters facing elevated prices for hotel rooms and flights, and with the challenge facing fans travelling to the Europa League final between Arsenal and Chelsea in Azerbaijan on 29 May.
Supporters will need a visa to enter Azerbaijan and London-based fans face a journey of more than 2,468 miles to Baku Olympic Stadium.
Klopp said: "How can you have finals in Kiev [where Liverpool played last year's Champions League final] and Baku? I don't know what these travel guys have for breakfast."
Liverpool and Tottenham fans will share 33,226 tickets for the Madrid final, which takes place in a stadium with 68,000 seats.
Arsenal and Chelsea fans will share 12,000 of 68,700 seats in Baku.
On Friday, Tottenham said they will open their stadium to full capacity to allow "as many fans as possible who are not able to get to Madrid the chance to come together for the match".
The match will be broadcast on four high-definition screens within the stadium bowl, with adult and junior tickets costing £15 and £10 respectively.
Tottenham manager Mauricio Pochettino said he is "suffering" for Spurs and Liverpool fans because of the cost of visiting Madrid, where the sides meet in the Champions League final on 1 June.
"Yesterday I was calling some hotel to try and book some rooms because I don't know if my family is going to be there, some family, some people from Argentina," said Pochettino.
"I wanted to book and it was so difficult and the prices are so crazy."
Uefa said its "recent experience" with finals in "comparable venues" meant "the number of finalists' supporters requesting tickets for a Uefa Europa League final can vary greatly from club to club".
"Of course, it is impossible to predict in advance which clubs will reach the final while the venue has to be chosen around two years in advance," it said in a statement.
"Taking into consideration the above and most importantly the geographical location and logistical capacity of airports in and around the host city, it was deemed that around 15,000 spectators would be able to travel from abroad (this includes finalists' fans and general public), with Baku as the main hub."
It added that "offering more tickets to fans of the participating teams, without any guarantee that they would be able to arrange suitable travel to reach Baku, was therefore not a responsible option".
"Based on these circumstances, for this year's UEFA Europa League final in Baku, 6,000 tickets have been made available to each of the finalists."
Fans team up to criticise Uefa
Liverpool supporters' union Spirit of Shankly and the Tottenham Hotspur Supporters' Trust issued a joint statement, complaining of a "measly allocation from Uefa" for the final at Wanda Metropolitano stadium, the home of Atletico Madrid.
The two fan groups called for a cap on ticket pricing, transparency over allocation and protection for fans to stop hotel and flight prices being "forced up".
"There needs to be transparency from Uefa and both clubs in how tickets are priced and allocated," the statement read.
"It is time to stop cashing in on fan loyalty. For many, the final is not a one-off event. It is the culmination of a season-long journey for fans, who have spent thousands of pounds already travelling to support their team, bringing the spectacle and atmosphere that is a key part of the game so prized by television."
Arsenal called their ticket allocation "disappointing" and said it presented the club with "extreme difficulties" for their Europa League final.
Arsenal Supporters' Trust endorsed the statement made by Tottenham and Liverpool fans, adding: "AST backs every word. We are working with them and all supporters groups to fight the disgraceful way that Uefa treats supporters. Not just at finals but at every stage.
"Uefa's treatment and attitude toward fans needs a fundamental overhaul."
Uefa's official regulations for both the Europa League and Champions League state the body "owns all rights relating to tickets and decides on the number of tickets to be allocated to the finalists".
The rules say ticket allocations "do not have to be equal" and add that Uefa determines prices along with the association of the country hosting the final.
Tickets not allocated to clubs will be split between the public, Uefa, national associations, commercial partners and broadcasters.
Face value seats for the Europa League final are priced between £26 and £121, while the Champions League showpiece comes in at between £60 and £513.
Liverpool and Tottenham supporters said face-value tickets at more than £500 were "exorbitant", and some tickets for their final have already appeared for resale on ticketgum.com priced at £5,500 each.
Rising flight prices have also attracted scrutiny, with Liverpool Metro Mayor Steve Rotheram tweeting Easyjet to ask why some prices had risen by 683%, adding the situation was "entirely shameful".
'Just about the worst location there is'
Chelsea Supporters' Trust described the 6,000-seat allocation as "totally inadequate" but board member Tim Rolls told BBC Sport fans were more angered by the difficulties in reaching Baku, which won the right to host the final over bids from Seville and Istanbul.
Rolls has booked to fly to Tbilisi, Georgia, before taking a seven-hour bus journey.
"Baku is one of the most inaccessible cities in Europe from the UK," said Rolls. "There are few flights and those there are are prohibitively expensive.
"The Chelsea and Arsenal £979 charter flight is ludicrously expensive and prohibitive.
"The people who have been to a load of Chelsea games and away from home - maybe 40 to 50 matches this season - simply cannot go. It must be about the worst location there is."
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