A free bet is not free money, and the difference is one stake

A free bet token pays the profit and keeps the stake. A settled winner on a 50 token at a price of +200 credits 100, not 150, because the 50 was never yours to get back — it was the bookmaker's, and it stays with them. This is the single most misread thing in promotional betting, and it changes what the token is worth by its entire face value.

The token exists to cost the operator less than it appears to. Handing out 50 in cash and 50 as a stake-not-returned token look identical in an advert and differ by a whole stake in the accounts. The mechanism is also what makes the token behave unlike your own money: with cash you would take a short price for a high chance of a small profit, and with a token that is close to the worst thing you can do.

It does not mean long prices are good bets. The token changes which bet extracts the most from the token; it does not change whether the bet is worth making, and the price is still the price. A token is a constraint to optimise within, not a reason to take a bet you would otherwise refuse.

What follows from that is less comfortable. Beginners spend a token on a heavy favourite because it feels safe. A 50 token at −500 returns 10 and the token is gone — nine tenths of its face value evaporated on the bet that felt least risky, and the risk it protected against was never yours to carry.

What to do with it. Before using a token, work out what it credits at the price you are considering, and compare that with what it credits at a longer one. If the token is stake-not-returned, the answer is almost always the longer price.