In Australia the MFC ukes seem expensive, as are others, because there is a 10% GST tax and because the shop owners claim high overheads. I have bought 3 ukes and several books direct from MFC over the years. In Australia this is the cheapest way to acquire an MFC product under $1000. You save the 10% GST which is not charged for items under $1000, and there are no shop overheads. The products are well known and come set-up ready to play, and you can keep the boxes which are the right shape and size and packaging for for long term storage (in your house). Its fairly safe to order factory direct and know that you wont need a set-up and if there are problems caused during transit, you can liaise directly with MFC to get them resolved. When you send your order and do the emails etc. you get to deal with the company owners in a lot of cases. There are no middlemen sales staff. Even if you live in Australia you get to deal directly when you order factory direct.
So if you are looking for a MFC uke, make sure you check out the prices for dealing direct with the factory via the MFC or FMM web-sites.
Also I recall reading posts on other boards from early in the century when the Flea and Mahalo U30 sellers were competing for marketshare in the low cost uke market in UK. I was never there, I just read the posts. The Mahalo sellers found a lot of problems with the Fleas, (Plastic? Ugh etc) and the Flea sellers found issues with the Mahalos (toys ugh). Much like we see on a UU thread at the moment which compares HPL Enyas with the MFC products, same marketshare competition. Of course now 10 or 12 years later, Fleas are still maintaining a good marketshare and the Mahalo U30s are not in production, and their replacements are not getting much respect. So if you live in the UK there is going to be a legacy of people talking about "issues and problems and plastic" in respect of the MFC products. Maybe they now are comparing to items like the Enya products instead of Mahalo products.
There is not much you can do about customs duties etc. so they are an added cost as is postage, which will always make imported ukes more expensive. If we get a trade war happening this will only get worse.
Flukes and Fleas have been in production since the 1990s, I think Jim Beloff started publishing his books around 1994, so maybe the MFC started around then as well. Going back to the question in the OP which is about durability of the MFC ukes, there is a very good chance that a uke purchased new in the 1990s is still in excellent working order. And 1998 was 20 years ago, so in the UK there has to be a few MFC ukes hiding in cupboards waiting for the right offer. This may be a way to access a MFC uke in good condition if you are looking in the UK (or anywhere really) and don't want to just throw money at postal services and customs duties for little return. In addition to buying a good condition used MFC product, you would also be acquiring a uke which is just going to be more and more collectible as time passes.
Note that the same thing will probably apply to 1990s and early 2000s Mahalo U30s.