I purchased on the 18th of December 2018, $18 USD which converted to £14.84 GBP (my local currancy), I'm aware that not exactly early in the project but I'm sure other people backed you a lot early for a similar price and it's close enough to the £14.99 full price. But then on release day you discount on Steam to £12.74.
I realise that you are discounting to gather sales and interest. But without this financial investment would you have got this far? Or so soon? I think indie developers forget that people paying for Early Access are taking 100% of the risk. If an EA game fails we don't get our money back, it's gone, the developer spent it.
It's also the case that we imagine that by buying direct from the developers that you get more of the profits as a 3rd party (like Steam) aren't taking any commission. By that token are giving you more support by coming direct.
Although we're happy to take this risk, it's a little insulting that even though backers took that risk on you, and in some case acted as unpaid Beta Testers, the people on the side lines get the rewards of a 15% discount. It's not a case of the money, I'm a well paid software developer and £2 isn't even a cup of coffee. It's the element of fairness and trust.
As a company you can't buy trust, you earn it. I, and anyone with an ounce of logic, will look at this and think "Why should I take this risk again?"