DawnGlare has 22 rares and 2 uncommons listed, meaning those cards’ prices are above average. Totaling these right now is $267.60 for 4 of each.
Conservatively (and excluding the basic lands), assuming each 31 remaining rare goes for $0.50, each of the 78 remaning uncommons go for $0.10 and every common is $0.05, that’s a total of $381.00.
And that’s a conservative estimate — there will probably be some rares worth several dollars and purchasing these cards individually would result in a good deal extra spent on shipping. The $400 MSRP is about right.