Can WizzAir force me to give my expensive carry-on into cargo hold?

You can keep it in the cabin if it is smaller than 40x30x18 cm. Otherwise you can't.

As we have limited space onboard, we cannot guarantee that all passengers’ hand luggage will be travelling with them in the cabin area of the aircraft. Only passengers with Wizz Priority will be able to bring their hand luggage on board subject to boarding procedures at each airport. The hand luggage of all passengers who have not purchased Wizz Priority will be placed into the cargo hold compartment of the aircraft and can be collected at the baggage belt in the arrival airport. If your hand luggage is smaller than 40x30x18 cm, you may take it into the cabin but it must be placed under the seat in front of you. Please note that only 1 such bag per passenger is permitted.

Source: WizzAir Baggage Policy

Life is strange, to protect expensive stuff you have to sometimes spend even more. I would buy the priority service if my carry-on was really valuable to me.

From Hanky Panky's WizzAir Baggage Policy link:

MY HAND LUGGAGE WENT TO THE HOLD AND MY MEDICINE/JEWELLERY/LAPTOP WAS STOLEN/DAMAGED. CAN I RECEIVE ANY COMPENSATION? DO THE 'EXCLUDED FROM HOLD BAGGAGE LIMITATIONS' APPLY TO MY CASE? If your hand luggage went to the hold and it was stolen or damaged, you can report your damaged/lost items upon your arrival at the Lost Luggage/Baggage Claim desk. We cannot compensate you for the loss of valuable items (items excluded from the hold) such as jewellery and laptops. We recommend you remove these items from your bag before giving it to the hold.

WHAT SHALL I DO IF MY BAG GOES TO HOLD AND I HAVE MY FOOD IN IT? We sell snacks and drinks on board, however, if you would like to take your own food, we recommend you remove it from your bag before giving it to hold.

CAN I BRING MY VALUABLES ONBOARD? Yes, you may take them out and bring them onboard, but you cannot bring a second bag.

It looks like they suggest themselves to take valuables out before giving the bag for hold.

With the new policy all passengers without priority have been told they need to put their baggage in the hold, no exceptions, on my four flights since the new policy. I could however always take out my laptop bag, so as long as it fits in the other bag from the beginning its not a problem to take it out.

OK, personal experience: I traveled about a week ago. I had a backpack that can be pushed to hand luggage size, and a small messenger bag with phone and documents, similar small items.

They did measure my larger bag to "personal item" size, and as it did not fit, I was told I need to get priority, or give up bag. Never mind that it contained camera, several lenses and laptop, buy priority or give up (I did mention the contents). I decided to buy priority, and was told that simply stand in check-in line (I was not aware about these requirements before, so did not buy priority in advance - I do not travel often with wizzair), and buy priority during check-in. When I got to the check-in guy, I asked for priority, he looked at me, at my bag, said: "is this because of bag?". When I said yes, he said "go, there is no time at the moment". So basically I was saved by lack of time.

But note, that they ignore the contents and might force you to give up or pay.

If it's your only carry-on, then I'd highly recommend just bluffing it out.

From their own WizzAir Baggage Policy

As we have limited space onboard, we cannot guarantee that all passengers’ hand luggage will be travelling with them in the cabin area of the aircraft.

Only passengers with Wizz Priority will be able to bring their hand luggage on board subject to boarding procedures at each airport.

These two rules are contradictory. One says it's hit & miss, the other says you have to have paid the extra.

In reality, they always ask for volunteers first if the plane is full.
Just don't volunteer, & if asked specifically tell them it's your camera bag, worth a fortune.
They will just ask someone else instead.

Data source, such as it is:
I never give up my camera bag. I fly with it half a dozen times a year. No-one has ever asked twice after I tell them what's in it - worst case scenario, I took out one of the big lenses, said "three grand" & their expression & demeanour changed immediately.
The bag goes up in the luggage rack with the rest of the carry-on, never in the kick-space.

Just to be clear, it is my only carry-on [unless I'm bringing duty free through on a return trip].
Additionally, it is larger that their 40x30x18 cm rule, but is inside the usual carry-on size of 55x40x23cm.

If you wanted to carry it on as an extra bag, then no doubt you'd have to pay for Priority.

WIZZ Priority

If you purchase the WIZZ Priority service (or you are entitled to WIZZ Priority with WIZZ Privilege Pass, WIZZ GO or WIZZ Plus bundles) your hand luggage will be guaranteed to travel with you in the cabin area, and you will be allowed to carry one additional small bag (a handbag, a laptop bag or a camera bag) that is not larger than 40 x 30 x 18 cm, and must be placed under the seat in front of you.

If you board at a Major airport such as London Luton and are able to guarantee you are one of the first on then they will most likely let you keep it with you. On the opposite end, if you are boarding at a minor airport such as Poprad-Tatry, they won't usually make you put your bag in the hold.

Therefore unless you can keep impeccable timing, I would recommend either shelling out for Priority or switching bag and keeping your valuables on your person in a large coat or jacket, rather than in a bag.