Bonus Buy RTP Math 2026: The Real Cost of Buying a Bonus in Slots
Bonus buy (or feature buy) options let you skip the base game and purchase direct access to a slot's bonus feature — for a multiple of your stake. They are legal in most markets but banned in the UK since October 2019. This guide breaks down the maths: what you actually pay, what the RTP means in context, and why the numbers are often misunderstood.
How Bonus Buy Pricing Works
A bonus buy costs a fixed multiple of your total stake per spin — typically 50x to 200x. A 1 spin on a game with a 100x bonus buy costs 100 to trigger the feature immediately. Providers calculate buy prices to reflect the expected value of reaching the feature organically, adjusted for profitability.
Feature-Buy RTP vs Base-Game RTP
Slot providers publish separate RTP figures for the base game and the feature buy. The feature-buy RTP is almost always lower than the base-game RTP.
- Example (Pragmatic Play Sweet Bonanza): Base game RTP: 96.51%. Feature buy RTP: 94.04%. The 2.47 percentage point gap is the provider's premium for the convenience of skipping straight to the feature.
The reason: the buy price is calibrated to be slightly above the expected value of organically reaching the feature, generating additional margin for the provider beyond the base-game house edge.
Expected Cost Calculation
The expected cost of a bonus buy is straightforward. For a feature buy with 94% RTP and a 100 buy price:
- Expected return: 100 × 0.94 = 94
- Expected loss: 100 × 0.06 = 6
Compare this to playing the base game organically to the same feature trigger point. At a 5% trigger rate and 1 per spin, you'd expect to trigger the feature after approximately 20 spins (20 total stake). At 96.51% base-game RTP, expected losses during those 20 spins: 0.70. The buy saves 19 spins but costs 5.30 more in expected losses — a significant premium for speed.
Volatility and the Bonus Buy Argument
The main argument for bonus buys is not improved expected value — it is variance reduction in trigger waiting. If you have a fixed session bankroll and a feature triggers rarely (1 in 50 spins), you might exhaust your bankroll before triggering naturally. A bonus buy guarantees the feature. This is a valid entertainment rationale, but does not change the worse expected value of the buy.
When Is a Bonus Buy Rational?
Given the lower RTP, bonus buys are rarely mathematically rational for value-maximising players. The exceptions are narrow:
- You have a specific session time constraint and want guaranteed feature exposure
- A promotion gives you bonus funds specifically usable on feature buys
- The game's base game has very low feature trigger probability and you don't want the variance
For most players, playing the base game at lower stakes and waiting for organic triggers provides better expected value per session.
Bonus Buys and the UK Ban
The UK Gambling Commission banned bonus buy features in October 2019. UK-facing operators must remove the feature or disable it for players. UK casino players will not see the buy option in the game UI. Most providers now ship dual versions of games — one with, one without the feature buy.
FAQ
- Is the bonus buy RTP always worse than the base game RTP?
- Almost always yes — feature-buy RTPs are typically 2-5 percentage points lower than base-game RTP. This represents the provider's premium for the convenience mechanic. Always check both RTPs in the game info before buying.
- Why are bonus buy features banned in the UK?
- The UK Gambling Commission banned bonus buy features in October 2019, citing concerns that they facilitate faster-paced, higher-stake play that is linked to gambling harm. licensed casinos must disable or remove the feature for players.
- Does a bonus buy guarantee a big win?
- No — a bonus buy guarantees you enter the feature, but the feature outcome is still random. You can buy into a bonus feature and get a low multiplier result. The RTP still applies: expected return is below 100% of your buy cost.