Although some of the first video projectors used conventional filament lamps, yours will have a discharge or metal halide type of lamp. The price of the replacement lamp you stated would be about right for an discharge lamp.

 It's not a straightfoward swap to put a halogen lamp in a projector. The power supply for the discharge lamp is current regulated, between 25 to 140 volts depending on the lamp. The lamp igniter produces a high voltage ignition pulse which would cause damage to the old lamp socket if no arc lamp is installed, and would blow up if connected across a kitchen spotlight bulb.

Halogen lamps produce much more infrared than a metal halide lamp of comparable size, and this will damage the polarising filters in the optical assembly.

Obtaining even illumination of the whole picture is more difficult than you may think. The colour temperature of the lamps is different, incandescent are yellow, and arc lamps are more like daylight, this will affect the picture.

Lastly the projector electonics monitors the lamp status, and shuts down if there is an error.

It's not an option unfortunately. Nice idea, but you may ruin a perfectly good projector trying.

It's an Optoma EzPro 610H

If anyone lives in the states (where they're much cheaper) and wants to buy and post as a "gift" to help me avoid import taxes, it would be awesome. If not, I may just buy one from the UK website and get another one when I'm over in Louisiana in March

The solution:

I thought I'd share this. I eventually went to a place on Tottenham Court Road (which has dozens of electronics stores) and after some discussion and haggling, managed to get a projector for £380.I'm now selling my old one (minus bulb) for £200 on Gumtree.  What I have now is maybe not as bright but it's far more suited to my situation, small room and needs. Effectively I've bought a new projector for (once I sell the old unit) less than the cost of a new bulb. I also checked and the bulbs for the new unit (whilst not exactly "cheap" int he normal sense) are much cheaper thanfor the other one.

I also have a projector with a dead bulb. I wish you luck selling yours, but it seems to me few people are prepared to buy such equipment, presumably because they can't see the thing working and check it for other faults. This HP model I have still retails for £1500, (somewhat inflated figure IMO), but sans bulb, looking at ebay sales, I think I'll be lucky to get £200. I was thinking of approaching a projection hire company or bulb seller to see if they are interested in making an offer, since they may be interested and would be able to test before parting with any cash.