It's probably pretty close to 2,500 ft of vertical but you can't actually ski that much repeatedly right now. Palmer runs from 7,000 to 8,500 feet, and that is entirely skiable, although the lower part is only linked through a snow-covered gully. Fortunately, you can hop on the Palmer lift half way up and do laps on the snowfield (the upper part) all day if you want to. The lower lift (Magic Mile) is about a 1,000 feet of vertical but until the seasonal snow starts filling it in, the last part of it remains bare, so you end up hiking 3-400 yards to get back to the parking lot.
It's also a good idea to check the weather if you are planning to drive down from Seattle. Because Palmer is so high and exposed on the mountain, it can easily get high winds, and if so they will shut it down for the day and there isn't anything to ski, aside from hiking up the lift area.
