It's important to note that there is no official number that is classed as keyword stuffing and every page/site is different. But in your example it's not a matter if its keyword stuffing or not. You should be making your URLs for your visitors and not the search engines.
Your unnecessary repeating the words, words such as 'new' are stop words and you no need to repeat the manufacturer or cellphone since its mentioned before.
is exactly the same as:
Focus on Keywords and what the page is about. If its a review then you use:
If its about 10 reasons why the gta800 sucks then you use something like:
Cater for your audience not the search engines. There is no need to repeat it more than once: it doesn't make it any more important.
Google has many ways of establishing what the page is about, URL is just one indicator of many. As long as you have the main 'KEYWORD' or Keywords you want to rank then the rest don't matter. Use the title, H1 and meta description for more in depth information. Short URLs are preferred, not only because they have higher click rates but also they are better to link.