When I built my home in '98 and had my well put in, the driller used a small 5 GPM pump to supposedly "develop" the well and then sold me a 10 GPM pump. The higher GPM drew in sediment because the well was never developed for the higher GPM. It also filled the casing with sediment and raising the pump didn't help as the sediment just came up higher. I had to get the driller back to flush out the sediment and put in some gravel.
You may have to run water faster and longer. If you have another hosebib, try running both of them. I would think that at the price you paid, the guy should come back and assess the situation and offer remedies. He may need to pull the pump and blow the well. He may need to overpump it to develop it for the higher GPM. He may end up putting in a dole valve to throttle back the GPM if the well continues to make sediment.
Do you have the original well record that describes the formation and total depth? If not, you may be able to get it from your County AHJ.