A guaranteed price contract, or a deposit against a future one
This is the distinction that matters, and Texas gives it a name you can look for. A guaranteed price contract fixes the price of the goods and services listed, whatever they cost when the time comes. A non-guaranteed contract holds your money and applies it against the price current at the time, and your family pays the difference.
Both are legitimate products. Only one of them does the thing most people think they are buying. The word to look for is “guaranteed”, and it will be on the document rather than in the conversation — if the contract does not use it, assume the price is not fixed.
Where the money sits
Pre-need funds are generally either placed in trust or used to buy an insurance policy assigned to the provider. Ask which, and ask what happens to the funds if the provider goes out of business or is sold. A trust arrangement and an insurance-funded arrangement behave differently in that scenario.
Ask also whether the contract is transferable to another provider, and what it costs to move it. People move house far more often than they change their minds about cremation.
What is not covered
Pass-through charges — death certificates, county permits, medical examiner fees — are usually not locked, because the provider does not set them. Cemetery costs are separate again. A pre-need contract that covers only the cremation is not the same as one that covers everything the family will face.
When not to pre-pay
If the published price is low and stable, pre-paying buys less than it appears to. Setting aside the money in a payable-on-death account, and leaving written instructions naming the provider, gives a family the same outcome with none of the transfer or insolvency risk.
Pre-paying makes most sense where it is being done for a specific reason — Medicaid spend-down planning, or removing a decision from a family who would struggle with it. Those are good reasons. "Locking in the price" is only a good reason if the contract actually fixes it.