We really get the short end of the stick when it comes to seating at football and baseball stadiums. Never can we have the opportunity to get the expensive seats even if we could afford them. My experience has been different though. There have been cheap seats all over the place except the limited number of accessible seats left, which are sometimes 5x the cost of where I could sit elsewhere if I had access (like getting up and walking ).

Has anyone had success buying the nosebleeds and exchanging them straight up for wheelchair access?

Here is what ADA has to say about it:

Many existing facilities may not have accessible seating in all price categories because of existing architectural barriers. Under the ADA, a venue must remove such architectural barriers where doing so is readily achievable. What is readily achievable ("easily accomplishable and able to be carried out without much difficulty or expense") depends on the venue's architectural structure and resources. In those situations where it is not readily achievable to remove the barriers in a part of an arena or auditorium, the venue must offer a proportional number of seats in an accessible location at the same price.
For example, Sections 221.1 and 221.2 of the 2010 Standards require a 1000-seat venue to have 10 wheelchair-accessible seats dispersed horizontally and vertically. The venue, built in 1980, has 200 seats in its inaccessible upper balcony where tickets are generally priced at $50. The total number of seats in the venue divided by the total number of seats in the upper balcony (1,000 divided by 200) is 20 percent. The venue must relocate 20 percent of its required accessible seating (in this instance, two seats) to an accessible location at the $50 price level (for individuals with disabilities and their companions). These seats must be in a comparably priced or better location. The venue cannot relocate the $50 accessible seats to a section where the tickets cost less than $50.
People purchasing a ticket for an accessible seat may purchase up to three additional seats for their companions in the same row and these seats must be contiguous with the accessible seat.