> If the worry is that future migrants might not pay their way, why not charge them more for visas, or make them pay extra taxes, or restrict their access to welfare benefits?

What do you do when after a couple of years those very same immigrants starting protesting and rioting for civil rights like equal access to welfare benefits, equal taxes, right to vote and attribute racism as a motive for denying it to them rather than the original policy goal of making them pay their way and not overwhelm the locals in elections?