The 1 to 10 Glide Ratio doesn't work at such high altitude of 50,000. It maxes out atmost 20-Km and above that its not optimistic. So you can get atmost 200km Glide and add on to a 200-Km range impartation initially by a Rocket, it would easily give 400km. The Booster need to be designed to burn slowly without unnecessary high speed and high altitude with as much low MTOW as possible.
if you want a cheap weapon that can give ranges of 500+km.
Then subsonic cruise missiles/drones are the best option as far as options go.
The new russian
The Banderol, also known as the S8000, stealthy cruise missile/loitering munition is a good example that, it blurs the line between cruise missile and drones.
The Russian name Banderol approximately translates to package, or small parcel, in English.
It can also be launched from male/hale drones and helicopters.
According to Defense Express report on May 12, the S8000 missile has a reported range of up to 500 kilometers and a top speed of 650 km/h
It has ~120kg warhead.
It is made from hodgepodge of cheap chinese and commercial grade western components.
Due to their commercial nature it's also Harder restrict those components.
It also uses a cheap commercial grade chinese turbojet engine.
the missile is powered by the SW800Pro jet engine, manufactured by Chinese company Swiwin and sold on online platforms like AliExpress and Alibaba for around £12,000.
test-news/russia-deploys-new-s8000-banderol-missile-built-with-western-tech-intelligence-reveals-8289
Lightweight, low cost, and reportedly full of foreign components, Russia's Banderol cruise missile has emerged on the battlefield in Ukraine. Lightweight, low cost, and reportedly full of foreign components, the Banderol missile could put Ukrainian air defenses under even greater strain.
www.twz.com
A newly unveiled Russian cruise missile has emerged as a deadly force in the ongoing war against Ukraine, raising alarm over both its battlefield impact and the failure of international...
slguardian.org
The cost entire this missile is estimate to be 150k on the low end and 300k US dollars on the high end.
It also has "gps"(

)guidance

.
Along with glonass, baidu.
Also has inertial navigation system.
Terrain following.
Along with made up of composites with radar cross section reducing shaping.
For comparison, Storm shadow/scalp has unit cost of around 1-1.5 million dollars.
Max range 550km, top speed 0.9 mach, warhead 450 kg.
Excalibur extended range artillary shell has unit cost of 70k-100k us dollars.