Short answer: the cheapest fully legal option for a fitness center is typically a business-tier streaming service — most affordable I found is Pandora CloudCover (Pandora for Business) at about $16.95/month per location (when billed annually). (pandora.com)

Why that is usually cheapest (and safe)

• Business streaming plans (Pandora CloudCover, Soundtrack Your Brand, SiriusXM Music for Business, Rockbot, etc.) bundle music plus the public‑performance licensing businesses must have, and monthly rates are low (Pandora CloudCover lists $16.95/mo per location annual; other services run ~$19–$27+/mo). (pandora.com)
• Buying individual royalty‑free tracks or using a consumer Spotify/YouTube/Pandora account can look cheaper up front, but consumer services are not licensed for commercial use (and using them can expose a gym to fines). Royalty‑free marketplaces (Envato/AudioJungle, Epidemic Sound, etc.) can be inexpensive for downloads, but you must confirm whether public‑performance/PRO rights are covered — often they are not unless you buy a specific in‑store/business license. (soundtrack.io)

Quick price-comparison (typical recent examples)

• Pandora CloudCover (Pandora for Business): ~$16.95/mo per location (annual) — includes licensing. (pandora.com)
• Epidemic Sound — offers business/in‑store solutions (license‑inclusive) and is commonly used by fitness/wellness businesses; commercial plans shown in examples around ~$19/month (varies by partner/region). (epidemicsound.com)
• Rockbot / SoundMachine / SiriusXM Music for Business: roughly $25–$27/mo per zone/location (varies by plan and add‑ons). (rockbot.com)

Other cost points to consider

• If you try to self‑manage PRO licensing (ASCAP/BMI/SESAC/GMR), combined fees can add several hundred dollars per location per year (and vary by venue size/use), so the cheap‑looking DIY route can end up costing more and is more complex. Many business streaming services include those PRO fees. (sound-machine.com)

Recommendation (practical next steps)

1. If your priority is lowest monthly cost + legal coverage: start with Pandora CloudCover’s $16.95/mo annual plan (or compare similar business plans). (pandora.com)
2. If you want more control over playlists or unique tracks, compare Epidemic Sound’s in‑store/business offering or Soundtrack Your Brand (they cost a bit more but offer on‑demand/customization and sometimes offline playback). (epidemicsound.com)
3. Always confirm the plan includes public‑performance (PRO) licensing for physical locations before you sign — that’s the main legal requirement for a gym.

If you want, I can fetch current plan details and exact monthly totals (including multi‑zone or annual discounts) for up to 3 services so you can compare side‑by‑side.