Could be the 3 to 6 mentioned by Connoisseur or just the 2 (which I'll run with). Then there's the 2 or more at the end of the year that he might put up.
If he's 30 points underpriced compared to when he's rucking, then there's at least 4* 30 = 120 points we are getting for free if we start with him. Normally you'd have to pay a trade to get into those points because it would bee later in the year and you would most likely have bigger fish to fry (or be low on trades).
In this case, you are being offered 60 points straight up with a decent promise of more down the line.
I'd say if you were going to get Jackson in at all this year then you'd now want to be starting him. He will not perform at his peak for a large stretch of the year though as he will be playing out of the square for a large part of it. Starting him might cost you value or high end points elsewhere.
What provides the best bang for your buck?
The extra uber in that one mid premium?
A couple of MPs and 100k? (You will get another rookie)
A fairly solid Top 6 forward who could provide extra ruck coverage late and will most likely get first ruck duties for a good 6 weeks?