lambda gets incredibly expensive for anything that approaches even modest usage levels. Once you exceed about 10 requests/second, you'd be better off with the lowest tier virtualized instances ($2 - $5/mo from most providers including AWS)
Once worked at a place that needed to do rapid crawls of websites on short notice and we saved a lot of money by moving from.dedocatrd instances to lamdas that we could scale out and down as needed.
How you use them is important.