Extra options in order form?

Hello, I have an order form in which I have a product say test product having price $30. Now I want to give user the second addon say subusers each subuser having price $10 per month and user can increase the value of subusers to any number. Can anyone please suggest me how to achieve this. Because on product options we can’t increase option’s value.

Unfortunately, the only way you could do this natively is with a product option drop-down.

Can you just offer an upsell which would be a separate product at the price you want for the sub-users?