The Insurance charge is £3.35/5.04€ per passenger/per flight, while the Wheelchair Levy is 33p/50c per passenger/per flight, according to Ryanair's page on fees, taxes and charges
The Wheelchair Levy has been attacked by disabled groups who claim people may feel resentful to disabled passengers for having to pay the charge. The The Telegraph newspaper in the UK has been critical of the charge. Disabled groups claim the charge need be no more than 0.02p (0.03c) per passenger (an amount the newspaper claims would still net the company more than 1€ million each year).
Ryanair chief executive Michael O'Leary countered this in the Telegraph article, saying that "We estimate it costs £25 [per person] to transport disabled passengers at Stansted, and we carry 1.5 million such passengers every year" and claimed that Ryanair "kept getting people who just didn't fancy the long walk to the plane and declared themselves to be in need of assistance."
According to the paper, Easyjet estimate carrying wheelchair passengers adds no more than 10p (15c) to the price of each ticket, a cost they absorb into the normal price of their tickets. More: Ryanair vs Easyjet Price Comparison.
Meanwhile, another UK paper, The Guardian, wrote an article critical of Ryanair's Insurance charge. According to the paper, insurance costs have come down since 9/11, while Ryanair insurance charges have gone up and that only a fraction of the charge goes on insuring the planes. Ryanair counter by saying they introduced the insurance cost at a low level after 9/11 and are "under-recovering." However, Ryanair refuses to comment on where the additional money generated by the insurance charge goes to.

