Why do companies look for alternatives to Toptal?

The two common reasons are cost and structure. Toptal rates commonly run $60 to $150 or more per hour, with a margin that is not published but is widely estimated at 30 to 60% above the developer's actual rate, plus a $500 refundable deposit, a $79 monthly subscription, and weekly hour minimums. And even at that price you are hiring an individual freelancer, not a team, so project management, code review, and QA remain your responsibility. For a short specialist need that is fine. For a multi month build, the premium and the management burden both compound.