$4-$500 for just the radio means pretty much any popular GMRS mobile is in your budget. It might be worth asking what your level of investment is for installation. The DB20-g mentioned above is what I have in my truck, plugs into a cigarette lighter. Get a cup holder mount, a mag mount antenna, figure out coax routing to your radio and you can be stood up in an afternoon. For a 50 watts mobile, you’ll have to do some wiring to the battery. For another antenna other than a mag mount, you’re drilling holes. Budget wouldn’t drive this decision as much as how much work will you do to install it.
And that’s all assuming you say mobile and intend to install this in a vehicle. If you want to install this in a home as a base station, budget for a DC power supply, and put aside more money for a mast, coax, and anything else you need to stand up an antenna.
Welcome to the rabbit hole.