Regular price for the non-TMobile customers is $20/mo.

From the linked page:

How much will it cost?

The beta is free for all. When T-Mobile Starlink launches in July, it will be included FREE on our best plan – Go5G Next – and available on other plans for $15/month.

Until March 1st, T-Mobile beta testers not on Go5G Next can secure an Early Adopter Discount of $5 off per month, reducing the monthly cost to just $10/month.

Verizon, AT&T and other customers can get T-Mobile Starlink without switching to T-Mobile for $20/month after the beta ends in July.