I have owned, in my 28 months of cycling:
Raleigh Record Sprint aka black fruity: my sister's old bike, so free to obtain. Spent ~£400 on new bits for it, some of which is now on wee blue floofy. Could have spent half that, but I wanted bits I could abuse.
Genesis Day-One Flat Bar aka wee blue floofy/wintersaurus: bought for £450, down from £600. SPD pedals, road slicks and studly tyres, plus recabling/blocking brakes has been about £200.
Raleigh Esquire aka the iron horse: bought for £50 in car boot sale, donated/sold for three pints to colleague. Must get round to Golden Rule to hassle her about putting owls* on the chain today. Brake blocks and new tyres for around the same as I paid for it.
Cannondale MTB, aka the MTBeam: given free by husband of boss at work in exchange for helping them move house. Something over £2000 spent building it in the late 90's. Had to recable gears and brakes and buy road slicks, so maybe £80 of my own money spent.
Genesis Croix de Fer: bought for £1149. Mudguards for £25-ish, I forget the after-CCE discount price at TBC.
CarryFreedom trailer: ~£200 from LaidBack bikes.
The MTBeam is a cracking town bike and trailer-tugger due to the 2" tyres gobbling up cruddy surfacing, and the ~15 year old Hope hubs, Deore XT gears and brakes still being head and shoulders above today's budget kit, but getting that bike was such a freak occurrence of generosity that I dunno if should count for this discussion.
If all I wanted to do was get to work/shops at a commuto-pootling pace, I would have been fine on the iron horse. I got very lucky: it's in excellent shape considering its age and was built right in the first place, but the fact remains I could have been on the road this whole time for under a ton.
But...I don't want to commute at a pootle. Partly due to those silly round glands I've been cursed to carry around in that hideously ugly wee bag, and partly due to my propensity for sleeping in, I wanted something I could hurl rather than ride, so when Alpine Bikes made me an offer I couldn't refuse, I said yes.
Then I got into Audaxy stuff and wanted a bike I could sit on all day. As a side effect, I've got a bike that makes commuting a genuine pleasure. That's not to say I don't still love wee blue floofy; it's just that in wintersaurus mode it's a PITA to push those studded tyres around, so for the next few weeks I'll have a ridiculously overspecified bike for non-frosty days.
To get back to the main question: is it really worth three or four hundred quid extra to have a bike I can hurl rather than pootle? Yes.
Is it worth a grand to have a bike I can hurl in sublime comfort with absurdly good brakes rather than pootle? No.
*She's from Derry and pronounces the word the same way as the hydrocarbon-based liquid.