I'll break it down for you in terms of how I would price it.
99 range would be worth 25-30m.
The rest of the combat stats+prayer would be 30-35m combined.
The 4 99s are worth about 55-60m (Fishing 20m, cooking 10m, hunter 20m+, Fletching 10m)
The rest of the skills should be worth 15-25m (77 mining, 73 agility, 60 herb, all skills 50+)
Then you have to take into account that he already has all the skills done for barrows gloves, a few of the "hard" quests done like MM, and full range/mele void.
The macroing minor should drop the price a little bit but this account is still worth a good deal more than what you think. If you think it should go for 100m at most then why did you even try to offer 15m?
Sorry for making all these posts without actually offering anything for the account, I just can't stand people that have no clue what they are talking about when it comes to account sales.