I work at a carrier in Switzerland, if I take the phone we push at the top of our inventory, the iPhone 17 Pro 256 GB:

Phone: 1099 (Apple's MSRP). 24-month phone plan, 50/month the first year, then 81/month: 1572. Discount: -300

Now BYOD:

Phone: 1067 at the biggest and most reputable online retailer. Near identical phone plan sold through our discount/virtual brand: 30/month i.e. 720 over 24 months (but you can leave anytime).

So even assuming you buy it on day 1 with zero discount from Apple's MSRP, that 300 gift costs you 852 CHF really.

Now if I look at our most agressive competitor, you get the phone for free if you spend at least 1752 on a 24-month phone plan.

They have a better phone plan at 15/month i.e. 360 over 2 years. BYOD is still way cheaper.