Yes only options installed by the manufacturer apply towards the MSRP for an eligible vehicle. The Cybertruck is not an eligible vehicle for other reasons.
Evidence: https://www.irs.gov/credits-deductions/credits-for-new-clean-vehicles-purchased-in-2023-or-after
"In addition, the vehicle's manufacturer suggested retail price (MSRP) can't exceed:
$80,000 for vans, sport utility vehicles and pickup trucks
$55,000 for other vehicles
MSRP is...
Got mine 11:30 PM EST. It really is out of budget for me at this point, but I was debating it. Only to just now realize it isn't eligible for the $7,500 credit. Argh!!