Is a dedicated development team cheaper than Toptal?

Usually yes, and often by a wide margin. Vetted dedicated developers commonly run $22 to $60 per hour compared with Toptal's $60 to $150 or more, with no embedded markup, no deposit, and no subscription. The total cost is lower still because project management, code review, QA, and cover for absences are part of the engagement rather than extra work for your team. The cheapest hourly rate is not the point; the total cost of ownership over the life of the build is.