Integrated devices
Some simulator products can provide useful practice or display functions without a separate gaming PC. That can simplify a starter room, although optional third-party simulation software may change the requirement.
Simulator technology · PC planning
Golf Simulator PC Requirements: What Do You Actually Need?
The launch monitor does not determine the whole PC requirement — the simulation software and the resolution you want to drive are just as important. Check the software you intend to run before buying a computer.
Start with software, not the PC
Choose your launch monitor and simulation software first, then buy to the software publisher's current specification. Requirements change, and a computer that is adequate for basic practice may not be the right choice for detailed 1080p or 4K simulation.
1080p vs 4K
Higher rendering resolution places more demand on graphics hardware. There is little value paying for a 4K projector and then discovering the chosen PC/software combination cannot comfortably support the experience you expected.
Allow for the complete room
Include the PC, cables, network connection, projector/display and software subscriptions in the budget. A launch-monitor headline price is not the finished simulator cost.