A vegetable Nariyar curry from Bombay Restaurant in Hillcrest.

When DoorDash started offering on-demand restaurant delivery in San Diego two years ago, I took advantage of free delivery incentives to try the service. I wrote about the convenience of ordering through an app, and the cash-free exchange at my doorstep a short while later.

The email campaign pledges free delivery

I observed that, while it didn't require a minimum order, it compensated with a higher delivery fee, going up to $6.99, pre-tip.

I've used the service a few times since; usually when I've been either too sick, lazy, or drunk to feed myself. But for the most part, I've avoided it due to delivery costs. Between delivery fee, tax, and tip, I was usually looking a $8-12 charge on top of food that usually cost no more than $15 to begin with.

Lately, DoorDash has been sending me a lot of emails trying to lure me back. And one particular subject line kept catching my eye: "Try a new restaurant with $0 delivery."

An 11-percent service fee, if you look for the fine print

I like zero. When it comes to delivery fees, zero's good. So I tried it again, ordering Indian food from the Bombay restaurant in Hillcrest. Sure enough, on the list of items tallied up to total charge for my order of vegetable curry and naan, the line item for Delivery read, "free."

However, the free delivery of my $17.90 food order still wound up costing an additional $7.36.

It took me a few minutes to piece together what happened. The Tip line of a DoorDash bill defaulted to $4. That's slightly higher than a usual delivery tip for an order that size, even after factoring in sales tax.

However, the information pop-up window subtly linked beside the Tax and Fees line revealed more than just sales tax at work here. By rolling my cursor over the small Info icon, a small messge popped up showing an "11% service fee that helps us operate DoorDash." In this case, a hidden $1.97. Added to sales tax and tip, this charge is what brought my delivery cost over seven dollars.

Initially, I was angry to see DoorDash sneak in what's obviously a delivery charge, and terming it a service fee so it could claim to offer free delivery. That's pretty sheisty.

However, when I looked back, the $1.97 was still lower than any flat rate I found when DoorDash launched. And that $4 tip is adjustable. Regardless how much an individual chooses to tip a delivery driver, that amount will always be a factor in delivery costs. I'm sure DoorDash hopes you do tip its drivers four dollars, but it can't truly control that part of the cost.

But it can control fees. I accept the reality that DoorDash is going to take a cut somewhere. When I think about it, I'd actually prefer the delivery app take a small percentage than tack on an exorbitant flat rate. And doing so is way better than adding 50 cents to the cost of individual food items (which I've also seen the service do in the past).

But if I have to accept this reality — that nothing is free — so do you, DoorDash. Don't peddle a $0 delivery charge, if you can't deliver one.