Top Formula One drivers are some of the best-paid athletes in the world, with the ones at the very top of the pay grid earning more than 1 million (approximately $1.1 million) per race.And although drivers are largely paid based on their racing ability, intangibles such as marketability are also taken into account by the teams when deciding who to sign and how much to pay them.For an illustration of just how much money a top F1 driver makes, in an interview with the official F1 website, Jenson Button was asked for his best tip to avoid stress at airports. His answer: "Fly privately!"Or you could just buy your own plane, like Lewis Hamilton:That said, there is a big drop-off between the best-paid drivers and the mid-level ones, and then again to those at the very bottom.Recently,Business Book GPand Spanish newspaperEl Mundo Deportivo published a list of estimated driver salaries for the 2015 season (h/t Crash.net), and that means it is time for our midseason value-for-money ranking.These rankings are not a definitive indication of which drivers are doing the most with the least. After all, it's not Fernando Alonso's fault he signed a huge contract with McLaren and was then handed a car that can barely finish a race.However, the rankings can give us an idea of which drivers might be undervalued or overvalued based on their performances so far. Last year, for example, in our end-of-season rankings, Daniel Ricciardo was the most undervalued driver on the grid. This year, despite receiving a raise and driving a less competitive car, he is still one of the best bargains in F1 (although he said he would trade the extra money for a better car,perAutosport's Lawrence Barretto and Ian Parkes).Here are this year's midseason rankings:The first thing to note is that this formula clearly favours the drivers with the lowest salaries. That is because, as noted, there is a huge gap between the highest- and lowest-earning drivers and also because there is a limit to how many points anyone can score, no matter how much you pay them.Lewis Hamilton may rank near the middle of the pack here, but Mercedes will certainly consider his salary good value if he wins them a second-straight championship.At the very top of the table are three of the youngest drivers on the grid: Max Verstappen, Felipe Nasr and Daniil Kvyat. This should not be surprising, as all three have turned in impressive performances throughout the season.Valtteri Bottas also continues to provide excellent value to Williams, sitting fourth in the championship despite his relatively small 2 million salary. If the rumoursprove true and he ends up at Ferrari next year, noted here by Sky Sports, expect a big raise for the 25-year-old Finn.In terms of the really big earnersanyone making more than 5 millionNico Rosberg is providing the best value. His estimated salary is about half of his team-mate Hamilton's, but Rosberg is just 21 points behind him in the drivers' standings.Looking at the bottom of the list, neither Manor driver has scored a point this year, so they are unrankedalthough it is interesting to note Roberto Merhi's tiny 50,000 salary, which probably reflects the fact that he is basically on a race-by-race contract with the team.Next are the two McLaren drivers. Both are former world champions and are being paid accordingly, but until they have cars that match their skill (and compensation) levels, they will remain at the bottom of the value-for-money rankings.Unsurprisingly, the star-crossed Pastor Maldonado comes in just above the McLaren duo, having scored points in just two grands prix this season. His team-mate, Romain Grosjean, is making the same 4 million but has scored almost twice as many points.With nine races remaining, there is still time for plenty of fluctuation in these rankings, and the list will be updated at the end of the season.For now, enjoy the last few days of the summer breaknext week, the F1 circus heads to Spa-Francorchamps for the Belgian Grand Prix.Follow me on Twitter for updates when I publish new articles and for other (mostly) F1-related news and banter:@MatthewWalthert Click here to read full news..