Unless seas are very rough you will not usually have a problem with motion sickness, regardless of the cabin location.
People are all over the map on cruise ship spending. Of course, it depends on how much you drink or purchase at the shops. We have members who spend less than $100 on a 7-night cruise, and those like me who can easily spend over $1000 on a 7-night cruise.
We look at spending roughly $100 to $150 per day for the three of us.
You should consider that an 'average' price for a drink will be $6 for a beer, and $8 for a cocktail or glass of wine. Some will be a little cheaper, or more expensive.