Hi, I'm working as pentester for last 2 years, and before about 5 years in software development and system administration. Actually the price very very depends on scope, if you really need to check 1 IP only, and that is router, so most probably nobody will can not hack it, if you update software in time. So pentest will not show anything. If you want to reverse engineering the router software - so it will cost much much more that 250, moreover more that 2500 :)
Maxim