ProFootballTalk has been keeping the world appraised to the salary cap that each team has remaining every few weeks and did so again this weekend. Your beloved San Diego Chargers have the fifth least amount of cap room left ($2.86 million), which isn't really outside the realm of normalcy despite many Bolts fans thinking that the team and its General Manager is cheap.
I think the Chargers get labeled as being "cheap" simply because they're not usually out there bidding for the services of the league's top free agents. However, the reason they're not is because for years A.J. Smith was having the best drafts of any team in the league. Instead of bidding for top free agents to cover holes left by bad drafting (as he was forced to do this offseason), Smith signed his talent to big money contracts to stay and used free agency for depth.
The rest of the division is in a slightly different situation. After years of bad drafting by the Chiefs, Raiders and Broncos, those teams abandoned many of their starters and brought in regimes that focused on drafting better. Good recent drafting by the Broncos and Chiefs have left rosters filled with cheap (valuable) talent.
Kansas City has the 6th most salary cap space ($16.54 million) and the Broncos still have the 11th most salary cap space ($10.87 million) after signing Peyton Manning to a big-money contract. The Raiders are where they are because they lack young, cheap (valuable) talent and the guys they pay big money to aren't exactly Philip Rivers and Antonio Gates. The only team with less cap space than the Raiders ($1.34 million) are the Ravens ($606,000).