You can think of the Madison Square Garden as having 4 concentric circles, each above the preceding one: the 100 sections, the 200s, the 300s, and the 400s.
Primary market prices (those at the box office) for sections 101-120 (painted in red above) typically start from $105 and can go up to $656, with the average price per seat being $169. These are the most expensive seats at the Garden and those closest to the stage.
Prices for seats in the 200s sections (blue) typically start from $105 and go up to $381 with an average price per seat of $135.
The starting price for a seat in the 300s sections (dark green) is $65 and can go up to $231.
The remaining seats in the 400s sections are all priced at $65 per ticket.
Prices in the secondary market are considerably more volatile and it is hard to establish a "typical price range" for them. Prices on resale sites can go above or below those in the primary market depending on how close we are to the start of the concert and the overall demand for tickets.