Software development costs are usually less than 1/3 of the total costs.
I just want to know the % amount spent on advertisement and if that is typically the 'primary' expense, it doesnt have to be actual amounts either.
As you pointed out, advertising is probably the biggest single expense. In one game we had a $2M development fund, and I learned they spent $3.5M on advertising.
I've seen similar ratios on expensive games, with development costs in the tens of millions and non-development costs about 2x more than that. A global advertising blitz in game magazines, web banners, in-store displays, promotions, and so on gets expensive very quickly. Just getting in-store product placement can cost millions by itself.
In the grand scheme of business, writing software is the easy part. Making it profitable is difficult.