I'm sure Bob's will be the best deal, but that machine mart one can be had a lot cheaper elsewhere.
Check eBay for ones that are identical, just not sold by machine mart...
Mine is an ebay clone at half the price, I've changed the grit valve pipework for bigger sizes and put a tungsten nozzle on it. Works great with 2x 3hp belt drive compressors but I need to cool the air to stop condensation carry over when blasting for a while.
Grit currently costs between £4 - £5 for 25kg bags depending if its crushed glass or copper slag.