The right question isn't which of the two is better
Between a ready-made program and an automation built on your process there is no noble road and no shortcut, they are two different trades, and the choice depends on how much your work resembles everyone else's
A ready-made product is born by looking at many companies at once and finding what they have in common, a custom automation is born by looking at yours and nothing else, so the real comparison is between how much it pays you to fit an average and how much it pays you to pay for what makes you different
The ready-made program, and its real advantages
Ready-made software costs less because the cost of building it has already been split among everyone who uses it, you pay a slice and not the whole job, and that is a gap no custom supplier can close with skill
Then it already exists, you try it, you see it work before you sign, and that takes away a risk almost nobody counts
There is a third advantage you only notice after a few years, the product is improved for everyone, so fixes and new features reach you too without your asking for anything, while an automation built for you only improves when somebody improves it for you
The price of all this is one thing only, you are the one who adapts, the product has its own idea of how the work is done, and if your idea matches you won't even notice, if it doesn't you start bending the process, or bending the product, and the second one costs as much as a custom build without any of its merits
Custom automation, and its real price
An automation built on your case does the work the way you do it, with your checks, your codes, your suppliers writing the amounts their own way, and it doesn't ask you to change how you work to please a menu
With programs that have no direct integration at all it's often the only workable road as well, because no ready-made product will ever talk to business software that offers no door to knock on
The price is that you are paying for one person's time, nobody shares your case with you, and then it doesn't end on delivery day, because it has to be maintained, programs get updated, portals move their buttons, suppliers change their forms
When ready-made wins, and it isn't even close
It happens with the jobs that set you apart from nobody, the accounting, the payslips, the signing of documents, the email, these are things where being original is a flaw and not an advantage, and where the market already has products that are mature, used and corrected over years
The check that tells you whether ready-made fits your case is brutal and useful, try it on ten real jobs, the awkward ones included, and see how many get to the end without somebody having to step in
The most common case is the one nobody talks about
The situation you see most often is not ready-made against custom, it's the ready-made product leaving you half the work to do by hand anyway
You buy the program, it does its part well, but somebody still has to take the documents out of a mailbox, check them and retype them in, or export on one side and import on the other every morning, and that piece was never covered by the product because it isn't its trade
There the alternative isn't replacing the product, it's automating the manual piece around it, and the two live together perfectly well, the business software stays the one you chose and the donkey work disappears
How to decide
Ask yourself whether the process we are talking about is your way of working or an obligation that's the same for everyone, and be honest in the answer, because the temptation to feel special is strong and it costs a lot
If it's an obligation, ready-made wins, if it's your way of working, that is the reason customers come back to you instead of going to your competitor, then bending it to fit inside a product means throwing away the thing that makes you money, and there custom makes sense
There is a third answer that fits many people, the process is ordinary but no product covers all of it, and then the choice isn't between the two roads, it's keeping the product and automating what's left over, with a monthly fee that covers maintenance as well
If you are also weighing up throwing the business software away and starting again, first read whether replacing your software is really worth it, because the data entry often stays exactly the same afterwards