Vercel's free Hobby plan is for non-commercial use only, so a paid launch on Vercel starts at Pro. Netlify and Cloudflare have free plans, but their terms don't say whether those can be used commercially.
The answer
On a paid plan, Cloudflare is cheapest at £3.74 a month plus usage, then Netlify at £6.74 and Vercel at £14.98. Netlify and Cloudflare can start free, but their terms don't say whether the free plans can be used commercially, so check first. For a non-commercial hobby site, all three are free.
Hobby (non-commercial) or Pro $20/mo
Vercel's fair-use rules say: "Hobby teams are restricted to non-commercial personal use only. All commercial usage of the platform requires either a Pro or Enterprise plan." So a business site needs Pro from day one.
Free (300 credits), Personal $9 (1,000), Pro $20 (3,000)
Netlify's terms don't say whether the Free plan can be used commercially, so check before a paid launch. Plans are credit-based, so a busy month can push you up a tier.
Free (Pages + Workers) or Workers Paid from $5/mo plus usage
Cloudflare's terms don't say whether the Free plan can be used commercially, so check before a paid launch. Workers Paid starts at £3.74 a month, and usage above the included amounts costs extra. VAT treatment isn't stated.
Monthly cost in pounds, from each vendor's pricing page. Lowest figures compared before usage charges.