Cheapest is a dangerous metric — some $2 services are scams, some $5 services outperform $15 ones. Here's what actually works for under $6/mo on an annual plan.
An IPTV service needs to pay for: CDN bandwidth (the biggest cost), server hardware, software maintenance, support staff, and any content-licensing fees (for licensed services) or reseller fees (for grey-market). The break-even cost to serve a single concurrent user for a month is roughly $3–4 in bandwidth and compute alone.
Services offering under $3/month on monthly billing are almost always either: (a) over-subscribed (they sell 10 connections per line and hope not all 10 log in simultaneously), (b) scams (take payment, ghost you after a week), or (c) resellers of resellers — each layer adds a failure point.