Selling at max can be a risky practice that may be detrimental. I would be careful about trying that. What you need to do to make some real money is to get alot of nbrs and become socially active, then you can raise your prices. Having lots of slots in your store with a variety of products is good too, dont fill it with all the same stuff at same price and quantities. If you did want to try high prices, only do maps, deeds, permits and rare parts like nails, paint, shovels and to lesser extent bricks, hammers, screws, wood, picks or saws. Otherwise you can sell at near max (90%) if you have hundreds of nbrs, then those who do sell at actual max may still buy from you.